Having trained players for 12 seasons I have come to certain conclusions:
1 - There are without a doubt sub levels since I have had players stop popping at the bottom end of potential
Well, I have been training players since season 7 and been a NT manager for 10 seasons and I just don't see it. You say without a doubt but there has to be some doubt since you didn't make the game.
Like I said before...during season 9 or 10 I asked about Trainer levels and if they had sub-levels and the answer was NO, and then I asked about Potential and sub-levels and the answer was NO. So you would think if they made a change as big as this(potential having sub-levels) that they would have said something or would have updated the user manual. As of right now, I will continue to believe that Potential has a soft cap and that a Superstar is just that a Superstar not an almost Per. Allstar or an almost MVP.