I have a similar setup, where I link the bedroom and the bath together.
Unfortunately, I've not found an easy way to use "whole house" grouping and ungrouping, so I've just done them all manually, so that I don't have to re-do the link between bath and bedrooms.
There's been a request for a long time for addressing this, it's gotten the normal response, i.e. we'll pass that along to the Dev team, without any commitment to actually doing anything. I don't actually take umbrage to this myself, having been involved in enough software maintenance processes myself, I recognize that priorities change on the fly, and sometimes by the minute, due to the vagaries of life and the ways bugs pop up at the oddest times. So I support their "we're not going to tell you what is on our roadmap for the next build" stance.
There's a thousand (or more!) ideas floating around these boards, most of which include the statement "it wouldn't be hard to do this", which I find amusing. But they've certainly got a significant backlog to work through, when they're not dealing with the Amazon voice control integration, the current PLAYBAR Dolby Digital bug, or the Spotify bug.
But it's good that you've posted your desire, and hopefully at some point, this issue will bubble to the current sprint, and get done. But frankly, I've got one or two things that *I* consider more important 🙂
Bruce