I have <5 years experience in the software industry and this is my first time doing QA.

Before the stories in a sprint move to UAT, I am supposed to retest every single story in ~1 day in an environment between QA and UAT. 

The purpose is that multiple teams have their own QA environment where they exclusively test their features. The extra environment is to make sure features developed by separate teams don't interfere with each other. 

This expectation seems surprising to me. I suppose this isn't technically an entire sprints worth of work, since test cases have already been written, but it still seems like a lot for one or two days. 

Is this normal/reasonable/typical for an agile project?