I don't really mind picking a younger player who is clearly better than the older competition. I can see why tiebreaks generally goes to the older player, but it's quite bizzare how obsessed our teams usually are with picking mediocre older player for our junior teams. Keep in mind, this is the national team, not a club rushing young player into an environment they won't prosper in.
I would actually say it's the opposite regarding your point about senior hockey in this case. Hillström has looked better than pretty much every other player in this age group at the senior level, and plays one of the most projectable and mature games(not the highest potential, but at this point it should definitely be noteworthy). How he(and Drott as well) doesn't even make the team, let alone behind Hermansson, is odd from any performance based assessment. Björck absoutely makes sense, but to me there is nothing Hermansson has done that warrants this. He is not even a clear top2 08, in fact I would say there a couple of more interesting players than him in his own age group.