I agree, the situation I described would only be a fold IF you knew opponent for sure had both a monster wrap and flush draw, AND you were playing no limit, seeing as any pot sized bet is giving you 2-1, you will never be in a situation on the flop where you're getting less than a third of the equity in the pot, so yes a fold would be silly here, but it would be theoretically the correct play if you were playing no limit omaha and you knew your opponent had a large wrap and flush draw. As to calling the flop to see the turn, what if the turn brings him a backdoor flush draw also.
http://twodimes.net/h/?z=636710
pokenum -o as 3s 9c 9d - 7c 6c jh th -- 9h 8c 2c 3h
Omaha Hi: 40 enumerated boards containing 8c 2c 9h 3h
cards win %win lose %lose tie %tie EV
As 3s 9c 9d 14 35.00 26 65.00 0 0.00 0.350
7c 6c Jh Th 26 65.00 14 35.00
In the end, yes one can create hypothetical scenarions in which one would not want to call an all in with top set; but this scenario would likely never happen in real life, or you would be unable to correctly read the situation correctly; so never fold top set on the flop or the turn with no straight or flush possible when playing pot limit.