Besides Greenwood and Williams, all the others were just pretty much given their debuts and thats about it. I wouldn't say that he gave all of them opportunities, nor that he should had because some are clearly not ready/good enough.
Minutes played in the last 2 seasons:
Mengi: 546
Chong: 327
Garner: 292
Laird: 112
Bernard: 90
Levitt: 90
Mellor: 25
Ramazani: 6
Galbraith: 1
I mean its not like those players are actively part of the squad as to call Ole to have gave them the chance. Most of those minutes were either in a "garbage" group game in the Europa League last season who had no implication whatsoever or in the lower rounds of the EFL cup.
Im not saying Ole doesn't work with youth, but I think if he's going to be recognized for youth then the mentioned ones should be Greenwood and Williams. The "debut" stat seems just like a checklist one. I mean 5 out of the 11 debuts were just really debuts and thats about it.