I don't see anything wrong or strange with sharing the information. It's natural to want to find out who is in the class - as a parent, you tend to learn who your child fits well with in a class, and different teachers have different styles, so it's nice to get a heads up.
But we don't do it at this time of year
Our school doesn't announce class lists until next year. In fact, the kids go back to their old teacher/classroom for the first week (usually only a couple of days), before classes are finalised.
We live in a RAAF area, high turnover of students. So the school chooses to wait, rather than tell the kids a class and then disrupt them by changing it again.