Dungeons and Dragons - YOU CAN'T SEE GROG!!!

That sounds like the kind of tactic an Ork from Warhammer 40K would use.
Which, in the case of the Ork, would probably actually work due to him being so convinced that he's stealthy that immediately after yelling that, his opponent loses the ability to perceive him while he's "sneaking" past and legitimately forgets he was even there.

Basically yeah. In fact, the reason that they're ridiculously powerful psychics, to the point they can force reality to agree with them, is partially BECAUSE of their immense stupidity.
Their too dumb to realize some things aren't meant to be possible, so they make it possible because they believe it will work.