Both times I've reached the end of a season, on the first day of the offseason all overall and potential ratings have changed. Most of the minor league filler guys are now 1.5 stars/1.5 stars, instead of 1 star/1 star. In a few days things go back to normal, but it messes up the player development report (it's full of every players' star rating increasing), and makes things confusing for a little while.
Here's my organization overview screen on the first day of the 2015-2016 offseason:
Previously, most of the 1.5 star guys in the minors had been 1 star. I didn't change any settings, although early in the 2014 season I did turn on the new relative ratings for just one day.
EDIT: I'm sorry, I tried to make the image smaller but couldn't figure out how.