I think the truth is, everybody does wish fulfillment RP at some point or another, and as some element of nearly every character. Not all the time, and not only. Same way everybody wants to win some. Of course they do.
Every so often, yeah, one runs across a player who really seems, from every angle you look, to be doing only wish fulfillment and want all and only triumphs and glory. But more often, it's just an accusation used to promote the idea that somebody deserves less consideration in a conflict. It is also very often projection. Abelard wants to roll, protests being simply declared to have failed, but Brigid will not get the glory if Abelard succeeds, so she says Abelard "just wants to win," or "just wants his character to be super-cool all the time." In reality both want to win and be super-cool, and neither wants only that all the time, but both are likely to suggest the other is greedy for wins and wish fulfillment and rejecting other play. Just how likely they are to make these accusations depends on individual temperament, individual mental state at the time, individual past experiences of such claims working or not, how much OOC-cooperative vibe/tradition exists on the game, and (as mentioned in the incentivizing failure thread) how confident those players are of getting more chances.