Also, this is completely unnecessary. MPROP_PERPAGE doesn't remove the exit button and while the .inc file says it's deprecated, it really isn't. menu_setprop( menu, MPROP_PERPAGE, 0 ) positions the Exit button at slot 0 and also removes the previous/next items IIRC.
I thought the same thing but I wrote a test plugin to verify. The exit option is indeed removed.