Devices linked to MS account - an oddity

Win10 21H1 build 19043.1526

I'm preparing to replace the motherboard and CPU on one of my computers. I usually use local account on them, but I switched to using my MS account on the one I'm going to upgrade and displayed Devices on my MS account to see what it showed. I was surprised to to see (in addition to the one I'm going to upgrade) two other computers listed - computers that are using local accounts. And least one of those computers shows "Windows is activated with a digital account linked to your Microsoft account" even when it's using my local account.

Cool, thinks I! I don't need to use my MS account on the PC I'm about to upgrade. So I switched back to my local account ... and the PC disappeared from my MS account. I tried switching back and forth a couple times with a couple reboots thrown in with the same result. This PC shows in my MS account only when I use the MS account rather than the local account.

But sometime during this futzing around another computer showed up in the MS account's list of linked devices: a laptop that also uses only local accounts. And that laptop hasn't been powered on today so I have no idea why it was missing earlier and shows now.

The devices that show in my MS account's list of linked devices are:

1. a Surface Pro tablet ordered from MS
2. a keyboard for that tablet, also ordered from MS
3. a homegrown PC that originally had an OEM copy of Win7 Home, upgraded to Win7 Pro, requiring my MS account and Troubleshooter to upgrade to Win10, and another use of my MS account and Troubleshooter for a motherboard and CPU replacement a couple years ago (so who know what MS thinks of that copy of Windows)
4. a Lenovo laptop with an OEM copy of Win10 Pro. (I don't remember ever using my MS account on it, but I guess I must have.)

At any rate, I assume I need to be using my MS account on the PC right before and after the hardware change in order for the Troubleshooter to get my activation to work, and I assume I can switch back to my local account once the re-activation is complete. But I really don't understand what I'm seeing on my MS account's list of linked devices.

I'm not sure, but it sounds like it may be pulling from something that is linked to the PC even though it's using a local account. Are you signed in to any Microsoft products? OneDrive, Office 365, etc?

As far as I know I've always had just one MS account. I've never had Office 365, don't use OneDrive, and don't use any other MS product that requires a login.

- - - Updated - - -

Things have gotten even stranger. On the computer in question I used my MS account long enough to do the hardware upgrade and then switched back to my local account. (Reactivation using Troubleshooter worked without a hitch.) However, that computer now shows in my MS account's Devices list twice: one occurrence is labeled "System Product Name"; the other is labeled "All Series". When I say "labeled" I'm referring to the information MS shows directly under the device name. I see it comes from the "System Type" in detailed data.

I'm now showing 6 linked devices none of which are currently using my MS account (and one - the Surface keyboard - obviously cannot be logged on at all). The information about the Surface and it's keyboard includes details about the purchase (made through my MS account) - warranty status, etc. It's understandable that MS maintains and displays that information regardless of the type of account used on the device. The other device data is puzzling but I'm not going to loose sleep over it.