That's absolutely right. For example you can create a player and adjust his stats to allow for him to have only say, a 90 OVR rating, when in actuality he could realistically be 2-3x better than any higher rated player.
For example you can make a 99 speed/99 str/99 elusive/99 trucking RB, lower certain other stats, and he's actually a monster, although the OVR wont reflect it.