This doesn’t really seem that complicated to me. Once a player has made up their mind they want out, they want to find out as quickly as possible what their real options are and make a decision where they are going next. Add to that the risk of getting injured by playing and practicing for an additional 2 games and 5 weeks, which would result in no options. And finally, with the Thanksgiving break and then semester break coming up it gives the kid time to consult with his family, visit schools, etc.
I get the abandoning your team angle, but in the world the NCAA has enabled, the timing actually makes perfect sense.