This actually had little impact compared to what Apocal said and what I pointed out above. Lords have never really thought too individually about wars and instead consider the factions state as a whole, I believe it has always been this way and the thing that changed was their sensitivity to how many wars they were willing to stay in (went from 3 wars down to 1).
Personally I agree with you that decisions should not be 100 to 0 always, but that wasn't the cause for snowballing being fixed (which means it can be changed without an impact on snowballing).