The only way to change this is without a custom HC I think. I'm just happy my Team Goals are based on my 3-4 Defensive Scheme and not the 4-3 scheme.
I tested this quite a bit when the game first released. Although each team might be locked into that defensive scheme for the in-game preview of the team's defense regardless of your chosen coaching schemes. I'll have to check now that I have quite a few teams with new HC's and different schemes in my 5th year in my league.
I'm using a custom HC with the Eagles and have an Attacking 3-4 scheme and 3-4 personnel archetypes chosen. When I play a game vs the CPU and it shows me defense on the preview it still shows me as having a 4-3 front instead of a 3-4. Everything else is 3-4 for me though. I think that is also why my 2nd DT's Team Goals are so high and also why my 2nd MLB's Team Goals are too low.