i just noticed i have an option i can adjust in defensive rules that i can't adjust with normal gameplan settings for some reason

here's the setting:

Personnel
------------------------------
Goal Line
Normal Defensive Backfield
Nickel
Dime
Quarter

is this intentional or am i missing something in my normal gameplan settings?

That's correct, the personnel when using normal gameplan settings will always attempt to match the offensive personnel. The rules give you a way to override that.