It's not "required" in that there is no rule that you must do so. if you hunt old threads, you'll find some from the past where it used to be a requirement that if you took the USMLE, you needed to release it to programs. That rule has been removed, so it's your choice.
What individual programs require may be different. Some programs may require the USMLE for DO candidates, some may highly favor those with USMLE scores but consider COMLEX, and some may be happy with COMLEX. You can pick and choose which programs you assign your USMLE transcript to -- although I believe the USMLE ID is visible on your application, so if it's there and there's no USMLE transcript and a program notices, they may ask you about it.
What to do is your choice.