P doesn't have to anticipate S's course change... S was changing course throughout, both in rounding the mark and the "deer" wiggle. P could make a compelling case that under 16.1, S should be DSQ.
P is not required to anticipate S's change of course, but she must respond to it - which she does not do.
Looking over the video yet again, I see boat H7(S) making two course changes. One is when she rounds the mark at time 0:32-0:34. The other is the "wiggle" at time 0:35-0:36.
During the first course change, boat M87(P) is still 2-3 boatlengths away. I believe that P had ample opportunity to keep clear (by slowing down, heading up, or tacking) during that time.
At time 0:35, however, P is committed to the cross and unable to keep clear by luffing. S makes a quick turn to her right but is unable to avoid P. S then turns quickly back left, taking contact on her bow. P is already not keeping clear so there is no possible way for S to give her room. If you insist on applying RRS 16.1 to the second course change, and conclude that S breaks it, then you should exonerate her under RRS 64.1(a).
Remember, the purpose of rule 16 is to protect a give-way boat from an overly aggressive right-of-way boat. It does not excuse an overly aggressive give-way boat for failing to meet her obligation to keep clear. A port-tack boat can't just sail into a line of starboard tack boats rounding a mark and say "oh, they should have held their course". The starboard-tack boats may not turn into P, but P can't use rule 16 to justify sticking her nose into a place where she isn't able to keep clear.
Regards,
Eric
