I think when game began it tried to reflect reality as best it could.
Youth going off to training camp was not a problem, as that 35 Days you could not have them in your team, really did not matter.
See back then, there was not a U-18 Cup or Leagues.
Now the game has progressed and catered for the U-18's it has become a very big problem.
You have only 21 youth losing a large chunk of them for 35 days is now a major error within the game I feel.
I guess the two solutions are 32 youth allowed or have the players at camp (youth only) allowed to play in your team.