No need to guess you are correct what I've notice is most base files using rosters already created work just fine however there was a process using the import/export feature to get them into a clean roster for naming players to avoid naming issues which works just fine....except for one thing the years pro.
The editor doesn't compensate or adjust for that player to player thus you get the years pro but they're not in sync with the player its suppose to be associated with, the only way to fix this issue is to put back the correct year associated with the player its suppose to be assigned to.
Other then that it works just fine, I mentioned this before along with Dolphin who reminded me of this awhile back concerning import/exports of roster files....check the data after the process and you'll see the years pro have to be re-assigned.
Finn hasn't updated the editor in awhile to compensate for this so you'll have to make the adjustment on your own for the correct years pro...that will solve the issue concerning the players stats when simulated.
Some guys don't mind seeing the years pro off a bit unless you intend on going deep into the franchise mode which make it a must have for correct numbers to associate with the players tenure years in the NFL.
The Boss....Lead Man
Rickster101