Yes it does because as I said, any manager in the world would play Varane because he was already so good. Its like how Mourinho was trying to potray himself as a believer in youth because he played Arjen Robben when he was young despite the fact that Robben had already teared it up in the Dutch League. You can't really say a manager is a believer in youth when he is playing already world class players who just happen to be young.
Regarding your second paragraph, as I said above, whether its right or wrong for the club is another debate.
He still does a lot of unappreciated work, if Mata was in that #10 position, maybe there would be more chances created, but would there be that balance? Would he be making gut busting runs back into his own box/full back position to make last ditch challenges when we're looking a little bit bare at the back/caught out on the counter? I don't think so. So long as Rooney keeps up that incredible work rate, and assists/scores 8 times in every 10 games say (he has scored 1, and fantastically assisted 2 in the 3 games so far), then he'll be doing a sufficient job I think.