I reckon these 2 going on loan is to ready them for next season. I think Pep sees the pair of them as our full backs next season. The only thing for me, is neither are tall.
I would be surprised if he saw the them as our first choice full backs next season. I expect that he will upgrade Maffeo to 2nd choice RB, behind a new signing who will play most weeks. But I agree that sending him out on loan would be good preparation for that role. I dont expect him to be playing week in week out next season, so getting a run of games under his belt now should be beneficial.