How much monk are you required to have?

Because there's a feat in Secrets of Sarlona, Tashalatora, that stacks unarmed strike, flurry, and something else with any psionic class you multiclass into. Monk 1/Psychic Warrior X/Slayer X is a pretty cool thing to play, and a lot more monkish than straight monk.

Also, some people like optimizing characters/classes to the hilt, theoretically what could be occurring here is the DM allowing this guy to do that but making the class a monk so he stays in line with the rest of the unoptimized party.