Did I said anything wrong or not true?
If you buy high potential drafters and decide to train them and save money to buy top players when you finish training of those drafters, you need to know that in 2027 you will have a problem because you WILL BE PUNISHED for training players for years by losing games because of your team's poor stamina in relation to opponents who do not train players, but can do stamina training.
I have had a level 3 or 4 nutritionist all the time for years. No player has ever improved in stamina. It only helped that they didn't lose skills often. But once in a few years it happens that a player loses a skill. With the highest level of nutritionist, it happens once every few years that a player increases his stamina. Cross training for 3 and a half years did not bring any pop up in stamina, and I have gym lvl 3.
Get yourself a level 3 gym and a level 6 or 7 nutritionist and you'll see your player's stamina pop without even needing to train.