Regardless multi-monitor setups exist and are well supported, so it's not hard to get both a 4k preview at 1:1 scaling and have plenty of room for controls by just running 2 displays.
It'd be nice to have it all - 5k, >60hz, and a decent HDR support. Even just 90hz would be a good improvement, but 120hz gets you zero pulldown for 24fps video! But alas that display doesn't exist. This display doesn't seem to really strike a good balance of what's achievable, it feels like a stop gap placeholder for the now canceled 27" iMac