No one starts with prop. Prop isn't required. Prop poll bonuses happen after a round of playing.
300 cards pre-auction. Less/more after prop. One card's worth is changed for each team. Prop bonuses then add in, based on whoever appealed to the masses the best, further distorting the value of a card. If I had learned that I was going to be forced to discard an extra card, perhaps I would have changed my auction bidding. 1 card is worth different to each team, in the end.
And note I've never been arguing directly against the event card, but the principle. Lowered vaults, lowered pre-R1 maximum card amounts and now a forced discard doesn't sit right with me.
There's also another point I could mention, but I don't know the future event cards to whether or not vault numbers changed because of event cards is unknown to me, in addition to results involving assassins.