Am I weird to have 2.3.1?
I wouldn't say "weird", but maybe in a small minority of owners . . .
If I remember right, 2.3 was released, and caused some issues for some owners, so Volvo dealers were given an update for anyone using 2.3 to be updated to 2.3.1. Sometime "shortly" after the 2.3.1 release, Volvo released 2.4, but 2.4 was only available from dealers. So you fall into the category of owners that were updated to 2.3.1 by the dealer for that short timeframe between 2.3.1 and 2.4's release.
IMO, if your car is running without issue, wouldn't be concerned and you can wait until 2.5 OTA is available, maybe wait to update for a couple of weeks to make sure 2.5 doesn't introduce new issues.