never heard of pet supermarket... guess there isn't one around here...
Anyways, chain stores have the same basic husbandry rules they have to follow, whether they are right or wrong. But each individual store does things a little bit differently. My job requires me to travel to many different petco stores. I cover about 20 of them on a regular basis, and occassionally a few others. Some know more than others, it depends on the individual employees... One store I was at let the ball pythons and red tail boas live together. I pointed out that they were mixed. There was a divider between the two enclosures, but it wasn't secure, and they kept pushing past it and ending up together. I was told that they do it all the time, and it was okay because in the store, the animals don't have enough space to establish their individual territory, so they don't fight. Um, okay. Even if that made sense, what if someone came into the store and saw them living together, and then tried to do the same at home? Big trouble.
Other stores I've been to do a pretty good job. That was the worst I've seen. Except for maybe the guy that tried telling me that bearded dragons were the perfect childrens pet, because if the kid forgot to feed it for a few weeks, it would be fine.