AppleCare One coverage issue with Mac using multiple User Profiles

Sorry this is about rambling, everything I found so far seems to be arguing about "adding my wife's Mac to apple care" and this is definitely not that so I want to provide all the info.

Yesterday, I had two Macs, a Phone and a Watch all on separate AppleCare subscriptions and I decided to unify them into AppleCareOne.

One of the Macs, the Phone and the Watch are always logged into my "personal apple account".

The other Mac, though it was bought by that Apple ID with my own money, is generally logged in with a "work" Apple ID. I have, essentially, a "work Mac" and a "Personal Mac", but they're both "my Macs". Find My on both Macs air set up for my personal Apple ID. The work Mac has a profile with my personal ID on it and that is what uses Find My.

Both Macs previously had separate AppleCare, both paid for by me, personally.

I'm labouring this point to try and be clear that this is not me trying to add a family members Mac under my AppleCare. They're both me, just with different hats on.

I converted the personal Mac, Phone and Watch over to AppleCare One yesterday and saved a little money. All good. I decided to add the additional Mac as well for £4.99 per month instead of £89 for the year, so figured I;d save a little money there too.

This morning I got an email from Apple insisting I sign in to "Work Mac" with my Apple ID or risk losing my coverage. I looked up the terms and conditions and it does indeed say if I sign out of my apple ID and in with another I can lose coverage on phone, iPad and watch. It doesn't mention Macs at all.

On the Mac, particularly with Fast User Switching, I can switch between users all the time. At no point am I (as far as I know) "signing out of my Apple ID", any more than I would be if I restart the machine and don't log in for a few days.

So I guess my questions are:

1. Is this just a glitch on switchover day from AppleCare to AppleCareOne?
2. Is it going to mail me every day even if I leave Personal ID logged in in the background and use WorkID in the foreground and force me to foreground the personal user, or worse, iCloud logout and back in again daily?
3. If I decide this is not worth the bother to save £3 per month, can I revert back to Applecare+?

On that third one, if it's possible, it's not at all obvious. I can "remove the device from AppleCareOne" but I dont see anything that would let me resume AppleCare+. It's a 2021 M1Pro so I need to maintain coverage continuously. If I remove and can't re-add, I'm hosed. It's my work Mac and I rely on it. I tried the "Renew subscription" button but it didn't seem to do anything.

Lastly, I'm in the UK, so US answers may not be applicable.

Thanks for any experiences you can share :-)

Alan