I mean, Its like every single MMO loot system and is mostly entirely common sense based. Item Drops into Pool. You either Need, Greed, or pass.

It will not drop out of the pool until the Timer hits 0 Or everyone Chooses an option. So if you get an item and 4/5 People lot it and 1 Doesn't select an option, It will not drop to anyone until the timer hits 0.

So yah, Like pretty much every MMO ever, an item will not drop to a player until all elligable participants chose an Option. Need, Greed, or Pass.