So we have AKA saying power crouch stab does work and you saying it doesn't.
By any chance did you try it without doing anything else with the sword first? This would indeed confirm, that this game runs on a modified japanese MM engine. Power crouch stab (and ISG) does 0 damage in japanese MM by default, but can be powered up like in OoT.
Fixing crouch stab in MM plus a few other changes were probably not done in japan but by the localisation team, since japanese 1.1 still has the power crouch stab. I would guess they used the japanese source code for this...
Escaping the forest using crouch stab doesn't work anymore, as already discovered.. tried it for about 20 mins, and we can hit it first time on N64 consistently.
Could be another hint that the MM engine is used. In clock town the guards have an invisible wall around them that actually also extends very far up. So backflipping over the Kokori that blocks your way in the lost woods as an adault, probably won't be possible either...