Can confirm it is "that fantasy martial art".
Your partner has to be in on it because otherwise you'd never have the opportunity to apply the technique; no one's going to let you e.g. just grab a wristlock off of their punch.
This is all down to how it is trained, training with no resistance leads to fantasy land bullshit.
Watch black belt level Aikido randori. Contrast with judo, wrestling, bjj sparring. The difference is obvious, one group is dancing in response to choreographed zombie attacks, the other is learning how to really apply techniques against resisting opponents.