Yes it is.
When did this supposedly happen?
He made 3 appearances for the u21s from January, the club can't magically stop him from getting injured and having to come off early in a match. He made 23 appearances at all levels with a further 6 on international duty despite being injured for over 2 months. He additionally appeared in behind closed door friendlies. That is literally plenty.
He didn't miss many matches though. PL2 has 26 matches. He was on international duty for 2, injured for 1 early in the season and 4 at the end. Missed 1 as he was dropped to the u18s. Made 13 appearances. That leaves 5 matches he missed due to being with the first team where he made 3 appearances, a more than fair trade off to play and train at a much higher level.
Find a better source then, he was injured all of April and May. It is also u21s not u23s. He was promoted to the first team, made 3 appearances, dropped back to the u21s made 2 appearances, went on international duty making 3 appearances and then got injured until the end of the season.
Playing regularly and getting introduced to senior football early has worked for all of our best youth players that have made it.