This has not been my experience. We run a bunch of GP drives, 1TB, 2TB, and 4TB, and I have not experienced them spinning down ever unless explicitly commanded

This has not been my experience. We run a bunch of GP drives, 1TB, 2TB, and 4TB, and I have not experienced them spinning down ever unless explicitly commanded to. They park heads for sure, but don't spin down. (These are normal GP, not AV-GP, never tried one of those.)