I don't think that's the reason. How could they prove that a player is based off of a specific NFL player?
I think it may have had something to do with the capabilities of Euphoria. Maybe it just didn't work with a wide range of body types? However I'm sure this is being fixed, especially with Red Dead Redemption using Euphoria for people and the horses. They recently had a video where they were using Euphoria on different bodies (such as aliens and just non-human in general), so I'm sure this is something that will be fixed by the next installment.