It's Costco policy to fit new tyres to the rear. Arguing with them won't get you anywhere as they're not allowed to deviate from their policy. Unless you have a special reason why. Someone one let them argue about the tyres needing to be rotated etc. and he let them blather on for a couple of minutes before telling them his rear tyres were larger than the fronts. They fitted the ones he wanted to the front.
Also, they won't fit tyres less than the manufacturers spec either, so if you go in and ask for H speed rated tyres on a GTI they won't fit them. Again, complany policy.
Being a stickler for the rules isn't a bad thing really, as so many people will try anything to get all sorts of tyres fitted, and if they're copped by their insurance then Costco will end up in the frame for fitting them. Easiest way with the rears - front thing is just let them do it, then swap 'em back on your driveway when you get home. As for the Quattro needing all 4, that's gonna be a hard one to pull them over on.