The issue with Huijsen instead of Calafiori is that he's not quite ready, whereas the club is in win now mode due to the past failed seasons. If Huijsen was just a project we could keep as 4th choice then fine but if someone is offering big money for him that could be used for starting players then the club has a decision to make. Soulé, to a lesser extent, may also fall into this category. He might be ready for Juve right away but may need time. Calafiori himself may not even be ready from the first minute, but he's more experienced and so less of a risk.
If we had a turnover of 700m then we wouldn't need to worry about these things and just put them in the squad or back on loan, but the club is still in financial difficulty so needs to think about players like these who would produce pure profit on the books.