Junos OS

group xx {
    ...
    import [ test1 test2 ];
    ...
}

policy-statement test1 {
    term deny {
        from policy [ default ];
        then reject;
    }
}

policy-statement default {
    term deny {
        from {
            family inet6;
            route-filter ::/0 exact;
        }
        then accept;
    }
    then reject;
}

policy-statement test2 {
	term allow {
	    from {
	        family inet6;
	    }
	    then accept;
	}
	then reject;
}

​

        from {
            family inet6;
            route-filter ::/0 exact;
        }
        then accept;​

group xx {    ...    import [ test1 test2 ];    ...}policy-statement test1 {    term deny {        from policy [ default ];        then reject;    }}policy-statement default {    term deny {        from {            family inet6;            route-filter ::/0 exact;        }        then accept;    }    then reject;}policy-statement test2 {	term allow {	    from {	        family inet6;	    }	    then accept;	}	then reject;}​

policy-statement default {
    term deny {
        from {
            family inet6;
            route-filter ::/0 exact;
        }
        then accept;
    }
    term last {
        then reject;
    }
}​

policy-statement test2 {
    term allow {
        from {
            family inet6;
        }
        then accept;
    }
    term last {
        then reject;
    }
}​

If it's not that, then the only differences between what you've got, and a working policy (correctly rejecting a default) is;
I don't use "family inet6" or "exact"

> show configuration policy-options policy-statement SUB_DEFAULT_OR_SHORT_V6
term MATCH {
    from {
        route-filter ::/0 prefix-length-range /0-/11;
    }
    then accept;
}
term LAST_TERM {
    then reject;
}

*Other than as "utility" policies, like...

set policy-options policy-statement ECMP then load-balance per-packet
set policy-options policy-statement REJECT then reject

group xx {    ...    import [ test1 test2 ];    ...}policy-statement test1 {    term deny {        from policy [ default ];        then reject;    }}policy-statement default {    term deny {        from {            family inet6;            route-filter ::/0 exact;        }        then accept;    }    then reject;}policy-statement test2 {	term allow {	    from {	        family inet6;	    }	    then accept;	}	then reject;}​

Hi!

So, I tried this using an EBGP connection.

Here are the configs:

skhan@vMX5> show configuration policy-options | display set 
set policy-options policy-statement BGP-DEFAULT-ROUTE-EXPORT from family inet6
set policy-options policy-statement BGP-DEFAULT-ROUTE-EXPORT from route-filter ::/0 exact
set policy-options policy-statement BGP-DEFAULT-ROUTE-EXPORT then accept
                      
skhan@vMX5> show configuration interfaces ge-0/0/0 | display set 
set interfaces ge-0/0/0 unit 0 family inet address 10.100.56.1/30
set interfaces ge-0/0/0 unit 0 family inet6 address 2001:db8::1/64

skhan@vMX5> show configuration protocols bgp | display set 
set protocols bgp group AS-64513 family inet6 unicast
set protocols bgp group AS-64513 peer-as 64513
set protocols bgp group AS-64513 neighbor 10.100.56.2 family inet unicast
set protocols bgp group AS-64513 neighbor 2001:db8::2 family inet6 unicast
set protocols bgp group AS-64513 neighbor 2001:db8::2 export BGP-DEFAULT-ROUTE-EXPORT

skhan@vMX6> show configuration protocols bgp | display set 
set protocols bgp group AS-64513 peer-as 64512
set protocols bgp group AS-64513 neighbor 10.100.56.1 family inet unicast
set protocols bgp group AS-64513 neighbor 2001:db8::1 import test1
set protocols bgp group AS-64513 neighbor 2001:db8::1 import test2
set protocols bgp group AS-64513 neighbor 2001:db8::1 family inet6 unicast

skhan@vMX6> show configuration policy-options | display set 
set policy-options policy-statement default term deny from family inet6
set policy-options policy-statement default term deny from route-filter ::/0 exact
set policy-options policy-statement default term deny then accept
set policy-options policy-statement default then reject
set policy-options policy-statement test1 term deny from policy default
set policy-options policy-statement test1 term deny then reject
set policy-options policy-statement test2 term allow from family inet6
set policy-options policy-statement test2 term allow then accept
set policy-options policy-statement test2 then reject

skhan@vMX6> show configuration interfaces ge-0/0/0 | display set 
set interfaces ge-0/0/0 unit 0 family inet address 10.100.56.2/30
set interfaces ge-0/0/0 unit 0 family inet6 address 2001:db8::2/64

Just to double check, here are your policies in hierarchical format.

skhan@vMX6> show configuration policy-options 
policy-statement default {
    term deny {
        from {
            family inet6;
            route-filter ::/0 exact;
        }
        then accept;
    }
    then reject;
}
policy-statement test1 {
    term deny {
        from policy default;
        then reject;
    }
}
policy-statement test2 {
    term allow {
        from family inet6;
        then accept;
    }
    then reject;
}

RESULTS

skhan@vMX5> show route advertising-protocol bgp 2001:db8::2  

inet6.0: 5 destinations, 5 routes (5 active, 0 holddown, 0 hidden)
  Prefix  Nexthop       MED     Lclpref    AS path
* ::/0                    Self                                    I


skhan@vMX6> show route receive-protocol bgp 2001:db8::1 hidden detail 

inet.0: 6 destinations, 6 routes (6 active, 0 holddown, 0 hidden)

inet6.0: 5 destinations, 5 routes (4 active, 0 holddown, 1 hidden)
  ::/0 (1 entry, 0 announced)
     Nexthop: 2001:db8::1
     AS path: 64512 I 
     Hidden reason: Rejected by import policy

Your policies are working, at least in JUNOS 21.1R3.11.

group xx {    ...    import [ test1 test2 ];    ...}policy-statement test1 {    term deny {        from policy [ default ];        then reject;    }}policy-statement default {    term deny {        from {            family inet6;            route-filter ::/0 exact;        }        then accept;    }    then reject;}policy-statement test2 {	term allow {	    from {	        family inet6;	    }	    then accept;	}	then reject;}​