I don't think it is just loyalty.
Xavi wants players who understands his ways already rather than those he has to teach them.
He is throwing same lines he used on Dest, his positioning etc.
I mean Roque came from a counter attacking team who barely keep the ball, of course he needs learning to how he should play in a team with 60%+ possession.
Loaning him won't make sense for Barca as he is unlikely to go to a team with same ideas.
But it makes sense for Xavi, as it will make Roque someone else problem. The "teaching" will come from next coach.
Xavi is showing his biases too though. And part of the job is maximizing the squad with the playersb that don't fit your profile. For example Luuk de Jong who he took a long time to utilisize. And even then, preferred not to keep.
Whatever technical traits that Ferran and Guiu have or show in train that Xavi may prefer. The flaw is that as a centre forward, Roque is superior to both. And has shown that superiority (while being in large a bit shire) over the pair with the first team too.
So there's that.
Lastly, Guiu had a huge impact for the B at the weekend, coming on and turning the game.
But watching that game the thought that got stuck in my mind, was how superior Roque is to that level and how many he would score.