Not standard here, but it's a mix. Same applies to other checkouts: so many people are doing the devil may know what, I'm terrible at picking the fastest queue.

Self check at Sam's Club at other club stores works in a one line per checkout way, where I am at least

Some places it's unclear, like Lowe's home improvement stores. Most people there sort of gravitate to a one-line-for-all-kiosks arrangement but there's often one douchebag who think everybody else is standing there for no reason and cuts in.

well, not in Jordan's hood