How in the world does better players = less growth? This isnt opposite day is it?
I think he is referring to with the players having higher salaries from being better players, it will siphon more $ out of the players' accounts, that they could otherwise invest into building up their arena, which has more benefit, than winning games sooner, or having better players quicker. I think.
There could be some other reasons for his saying that as well.
But, if that's the case, maybe a short "tutorial" could be added for new managers, explaining stuff like the transfer market, arena building, staff acquisition, etc.