[FireBeyond]

> that you can't get full resolution on some Macs

This is one area that Apple definitely does not "just do stuff right". Display Stream Compression has been broken (for Intel Macs) - and by broken I don't mean 'suboptimal', but "completely nonfunctional" ever since the first beta of Big Sur, and is to this day - is a well-known, documented issue (many users, multiple GPUs, differing monitors), though Apple has yet to acknowledge it.

My 2019 Mac Pro cheesegrater could, under Catalina, drive 4K monitors in 10 bit HDR at 144Hz.

As soon as Big Sur was installed, your options became HDR@60Hz or SDR@95Hz. Turn off DSC in the monitor and you get the DP1.2 bandwidth.