How can you say it is 'not correct' and based on randomness from what you showed above? You based your conclusion only on one case where you compared the value of the 6-star player to the value of a 5-star 19 y.o player and a vaguely estimated expected value (60M); you did not even buy the player to test to see if he is near the same level of speed of progress as the player he was recommended to replace. What values (with respect to what level) you are making reference to when saying this player is a slow trainer? Wage value also must be considered. The ratio of the market value to the wage value is a better indication of the speed of progress a player has before he is bought. The DC/DMC and MC has no relation as such. Is or was the 20. y.o DC like the MC? You need to buy the DC/DMC and compare his speed of progress to the 20 y.o DC when that same DC was 19 y.o and had around the same % quality in the attributes that were trained (the average should be in the same star-level), then repeat this procedure for atleast another (different) case, and post all the results if your aim it to prove that what I posted was 'not correct'.
The only thing that can be said from the above pictures you showed is that the MC might be a faster trainer than the DC (provided that ratio of value/wage is higher too, which cannot be verified from the pictures above). Keep into consideration that there are very fast trainers and those usually have the highest training factor (market value to wage ratio). Your 20 y.o DC might not be one (not all token-bought youth academy players are very fast trainers), but still is a fast trainer (if what you said about him about his speed of progress is correct) and the same is expected for the 19 y.o DC/DMC that was recommended as an improvement over him unless something has been changed recently.
I can understand your point with the value comparison thing but go read from that post (https://forum.topeleven.com/tutorial...tml#post640043) and further on from that post in that same thread (https://forum.topeleven.com/tutorial...ainers-92.html). I bought some of those players, made tests and posted about them there.