It was set down by Pep. He helped put in place a plan for players from B team to first team squad that had them being leaders in B team as important step in developing the before promotion.
Bascially off the back of Bojan failing and thinking he missed a step.
You have no idea how many games Pep would have played him and Pep was not calling up young players from B team as much as is made out.
Alena is a leader in the B team already. Clearly the best player in the team. No reason not to call him considering he'd be the 2nd best playmaker after 33 years old Iniesta.
Bojan failling is not any more relevant to this than Dembele making it big at 18-19. Some players need more time, some break out right away. But because some players are so good that they make it very very fast, you need to give them that chance. Maybe Alena becomes a starter by the end of the season a la Mbappe if he's given the chance. Just the posibility that he could be an Iniesta level midfielder should make Valverde give him a chance faster than you'd give a chance to the likes of Bartra, Montoya, Palencia or other good but rather ordinary Barca talents we've had in the past.
18, 19, I don't care. If he shows quality and deserves a chance, he should get it. Once he gets a couple of games we'll see how he reacts to it. If it's an exceptional reaction, he gets more and more chances. If it's a normal good reaction he gets some chances here and there. If he accuses the pressure, he players for Barca B until the end of the season. But at least you ask the questions.