"Hoovering up talents" can clearly be expensive. Both in compensation/tribunals, but also wages. Personally I've thought for some time that youngsters getting big moves and big wages early can hinder their development as it gives them a sense of having made it already. Our approach keeps wages down, perhaps not only for the immediate financial benefit of the club, but it makes our youth squads perhaps a bit more hungry?
I'm also not convinced that those gaps you talk about at u21 level is a problem. You describe playing players "out of position", but these players are so young that even knowing what their best position will be is difficult. And even in those cases where one knows the experience of playing different positions can be important. This is a lot closer to the Ajax total football model that produced Vertonghen and Alderweireld for me.
I also think having too much competition for places at that level can be detrimental. It's important that the youth players see a potential path into the first team, and it's important that we able to actually give those young players game time. Having too many players fall by the wayside, or too many players competing for first team football can have a negative impact on motivation imo.