Maybe, but whether he is 18 or 22, its a fact that all kids develop at a different pace. You should never sign someone "just" because they are 18, some are done growing when they are 14 and others when they are 20. If Moukokou was indeed 18 y/o, we can certainly rule out that he has any physical "youth growth" left in him anyway. Same with Bellingham. Bellingham is 19 y/o. He was at a stage in his development when he was 16, that many others hit when they are 20. You shouldn't buy Bellingham either, expecting him to be a high World Cup level of player at 19 y/o who therefor per automatic will be much better when he is 22. Any player can always develop, but never at the same rate as they do during that growth spurt at
My point is just, in any event, we must do our due diligence on this kid and evaluate how good we think that he can become. This is a kid who broker records at the U17 level when he was 12. 6 years later, he isn't going to grow physically. He is what, the same height now that he was when he was 15? Some kid can easily grow 3-4 inches after their turned 16. A kid like Wayne Rooney who was as developed as he was at 16 y/o, was of course never going to become like 6'3. It all comes down to whether we think he has enough ability and growth potential today -- regardless of his age. I just don't see how it should have any impact to be honest.