Yeah Costco return policy! I was in line returning something and recognized my Wurth salesman.He was returning a desk shelf unit on two dollys, some of it assembled and some of it in garbage bags all busted apart and holes punched through the back with a hammer for cords and they asked him why he was returning it and he said he moved into a new apartment and it didn't fit.
I have seen guys come in with battery's and no testing required, grab a new one or we will refund your card.
Bought an inverter genset and used it one summer. Didn't really like it and they dropped the line the next year but... no problem!
I wouldn't worry about Costco fine print! And purchase records are on your account, no receipt necessary.