Yes, to be eligible for a school’s grants, many will ask/expect parents info. And it sounds like for HPL, parent info is required as well.
However, for Federal Direct and Federal Grad Plus, parent info is not required.
Sounds like a few grad schools just routinely ask for parent info or merit and other considerations…but I am certain that if the student said, “My parents won’t provide info,” the school would just say, “ok, but you’ll only get fed Direct and fed Grad Plus” loans.
The OP can ask his school if parent info is needed for merit or some other reason.