Answer: It does, changing your wife "stance" will change the propability distribution during the event.

It is a bit more complex than that as several events have pre calculated the results of the choices before the player picks the option through the calculus being done in the immediate section of the code. In these cases changing the spouse bonuses does nothing.

Anyway, in plenty of events modifying the bonus the wife gives does indeed help the player. My view is that if someone wants to use that cheesy tactic, more power to him/her. There are plenty of cheesy tactics to be abused by the player in CK3 (or other very complex game for that matter), so, if someone wants to use them, it is their game, certainly not mine. If someone wants a more mature and fair experience, simply avoid doing that trick.

Bottom line, I am not going to comb the whole Dark Ages code to pre calculate every instance where player stats are involved. It would take a very significant amount of time and would not be fun at all.