There are two different situations here. The one in the ISAF precedent which Brian raised originally where PL doesn't need to tack or alter course to avoid S but PW does - and where PW can demand water from PL to allow him to cross behind S. The other situation is where PL does have to do something to avoid S and can either bear away behind S (and must still give PW room to do the same) or can choose to hail PW for room to tack - in which case PW must give PL room to tack. PL does not have to bear away behind S even if PW wants to go that way.