Well Jose does like a record so nobody should be surprised that he threw in a couple of 16 year olds into dead rubbers. It's what he does next with them is what is important.
As for our other managers, just think back to what ages Kane, Dele, Bentaleb, Davies, Dier, Eriksen, Mason, Walker, Lamela etc were when they were first quite prominent in our first team setup. Spurs have never been shy using the U21's and all our ex managers have given guys a go in their managerial stints. They didn't get 9 subs either to have the best of both worlds.
Saying that, we need to be patient and find out with Jose whether he will eventually shape the squad to include more U23's. He may not create the monster like he did at Utd where over 50% of the squad were in the 28 and over category. He may do it the Spurs way given time.