There is no such thing as a guaranteed starting spot for a young player, not in Serie A at least. For that reason I can understand moving to a higher Serie B team. Besides, the likes of Insigne, Verratti and Immobile all played that season in B with Pescara around the same age. Lots of 20 year olds have.
So did Jorginho, Dybala, Barella (a half season), Spinazzola (had a half career in B) and some upcoming players like Castrovilli, Tonali and Pessina. It’s not a shame, just a pity that it becomes difficult to follow his progress. Many players had a important year in Serie B.
Its important that they play and that they play at the right level. Personally I’m still a bit stuck between the idea of leaving him on loan or keeping him and hoping for a success, but 2 consecutive seasons on the bench would practically destroy him.