Hello,
If I understand Your question correctly, You want to know what happens if:
1/ 1st BGP Update with Flowspec NLRI with src ip 0.0.0.0, dst ip 0.0.0.0, proto tcp, dst port 22, action drop arrives at the router1
2/ 2nd Update arrives at router1 with exactly the same BGP Flowspec NLRI : src ip 0.0.0.0, dst ip 0.0.0.0, proto tcp, dst port 22, action drop
Well, these 2 updates are not supposed to arrive from the same source because they are identical, and BGP does not do periodic restransmit like IGP, but if they do arrive, it is a NOOP and by default oldest BGP update is preferred if such 2 updates are no different.
Now, if You want to know what happens if both updates are identical except that the action is different - e.g. 1st Update action is drop, 2nd Update action is anything but drop (redirect or remark) then according to BGP rules, the 2nd update is preferred, and 2nd NLRI replaces 1st - the 2nd Update is considered as implicit withdrawal for the 1st.
If Updates 1 and 2 arrive from different sources (e.g. from 2 Route Reflectors) then normal BGP path selection algo applies, and worst case it will be down to a router-id comparison.
So, in a nutshell, the rules You cited are applicable if there is ambiguity in BGP Flowspec NLRI and longest/most specific NLRI wins. E.g. if router1 receives 1st Flowspec NLRI with "src ip 0.0.0.0, dst ip 0.0.0.0, proto tcp, dst port 22" and 2nd NLRI with "src ip 0.0.0.0, dst ip 0.0.0.0, proto tcp, dst port range 22-23", then 2nd NLRI wins because it has longer "dst.port" string.
Hope this makes sense.
HTH
Thx
Alex