I'm not trying to be dismissive, but I'm not always sure if peope get the phsycology of how having multiple teams within a club works.
I often use this example but our cricket club has 2 teams. I got promoted from 2nd to 1st last summer, and then you are in that squad. You don't tend to just stop back down if you don't make the first team for a week. It gets set in stone a lot more. The 1st team captain takes the view that if he rests me, he wants me me rested for his team, which takes precadence. The 2nd team fulfils a different function for the club (as a reserves team does too).
Unsworth gave some telling quotes the other day on Small, saying that Nkounkou is an example of moving froward, he was with Unsworth for 2 weeks and then the first team. Going back and regularly playing for the reserves isn't commensurate with that. He will be training with the 1st team squad and it's how he will be viewed. It is a but unusual, that those who will often criticise Unsworth for playing older players, will also criticise him for not taking down lads who've been promoted to the 1st team squad.
As a final aside, Nkounkou is very much 1st reserve currently. He may well be 1st reserve for the entire back 4 (I mean probably not, Kenny is, but maybe). It may be that if Mina or Keane get injured the plan is for Godfrey inside and Nkounkou on. There is a lot of games coming up, and Ancelotti will want him at his disposal, and importantly the lad himself will not want to be risking injury or fatigue by wasting time playing for the 23's.
Hard though it is, you just have to trust people a bit on this. We are not actually that bad at bringing through young players and actually quite well regarded for it. There are many criticisms of the club, and even youth development, and a criticism of why he hasn't played more 1st team minutes, but him not dropping down on Monday night head of a Wednesday-Saturday fixture schedule isn't one of them.