My daughter had a 28 and a 3.79 GPA (don't quote me on that, I forget the exact GPA). A ton of AP, Honors, CE, two sports, year book editor, etc. etc. etc. Being outside the 25-75 range for GPA, but in it for ACT, we submitted it and she was not accepted.

Anecdotes about former admissions people refusing to say exactly what scores to submit but that "there is no reason not to submit a 30" were shared here. Looks to me like most people did a calculation and if their GPA was 3.9+, they didn't submit ACT even if it was pretty good (like in the range you suggested).

BTW, my daughter is going to BYU anyway. . .