Yep, the practical difference between a hidden higher privldihe level and another random coprocessor on the system bus which can send memory writes to your core's internal MMIO region (common on ARM based SoCs, anyways) is quite literally zero. If you can write arbitrary physical memory, the entire system is cooked (well, mostly, but RIP SGX). IME is no worse than random DSP, ISP, ML, etc. cores on your average SoC in terms of its privilege in the system. Don't miss the forest for the trees.