Windows10 feature upgrade 20H2 did not allow reversion option

Background
Feature upgrades seem to have a habit of breaking things, usually attached devices. So when I installed win10 earlier this year I created a checklist to check that all the attached devices I use still work, to be run as soon as possible after any feature upgrade was done. Part of the checklist is a check on the reversion option . . . which I have had to use previously.

As a further precaution, I don't upgrade a feature for several months after the upgrade is released - got burnt too many times with prior versions of windows upgrading immediately and then finding there is a bug in it all - that I wait a month or 3 after release (so that the obvious bugs are caught by the eager early adopters, and fixed before the mainstream gets going) before doing it.

What happened with 20H2?
It was generally released in mid Oct 20? I upgraded to 20H2 after 2 monthly patches (nov and dec) on18 Dec. Checking the reversion option, it was not allowed - because it said I'd installed 20H2 on 1 Sep 20 and the 10 day option had elapsed. Several screenshots here:
- the feature upgrade completed details page, which actually has the date of upgrade in the page. I marked it up with the reversion not allowed item. My aim in marking it this way is to expose the dates of upgrade and that reversion should have been allowed.
- the windows version page, which gives the 20H2 upgrade date of 1 Sep 20 - which was the date I upgraded to 20H1 or 2004

So clearly the left and right hand of this 20H2 feature upgrade don't talk to each other. I've feedbacked'd it, but since there isn't ANY mechanism to attach images without going thru an extensive privacy-invading list, I just said a) there should be a way to attach images without that, and b) there were images available if MS wanted them.

Any thoughts on why this snafu happened??? And how to avoid it again?

It was explained to me that because this is a minor revision and not much of the main code is changed and just features were activated that the date that is shown is the date when the major revision which is 2004 was installed is shown . Mine shows the date I installed 2004 even though I am running 20H2 now .

Thanks to all, interesting variety of replies . . .
So, I'm not the only one using 20H2 that is showing the 20H1 install date. The explanation certainly makes a mockery of the marketing hype about the upgrade. Microsoft: inconsistency and unreliable is thy name.
Nope, my checklist worked fine and I don't want to revert, but the inconsistency of this situation (revealing MS policy claims as the fictions they seem to be) warranted some mention in these forums. IF however, something had broken and I had wanted to revert - the only option in my case is recover from a backup of the C drive - which is a preliminary part of the checklist, now with text boxes, alert colours, underlines and emphasis. Not only is recovery faster than a new clean install, but there is zero chance of breaking things; something a new install always does.

Davidk said:

Checking the reversion option, it was not allowed - because it said I'd installed 20H2 on 1 Sep 20 and the 10 day option had elapsed.

20H2 and 2004 share a common set of system files, and cumulative updates. The update from 2004 to 20H2 is done by installing a small enablement package to turn on the dormant 20H2 features that were already in the 2004 system files. The date of your OS install is therefore still the date 2004 was installed. No system files were replaced or change by the update to 20H2 and no windows.old folder was needed as the system files are still the same ones that 2004 installed.

That's why you don't see the reversion option, there is no old system to revert to - it's still the same system.

If you want to go back to 2004 then all you have to do is uninstall the enablement package KB4562830. It installed like a cumulative update and can be uninstalled the same way you'd uninstall any CU. You do that in the Control Panel. You can uninstall it any time you want, there's no 10 day time limit for this.

AddRAM said:

Mine shows 20H2 was installed on 9/12/20, your install date 1/9/20 is rather strange.

Your date is in US mm/dd/yy format, the OP is in Australia and is using dd/mm/yy format.

Thanks all. I did manage to find that "enablement package' KB4562830, but it took a few goes to get the right items clicked.
I still think MS has broken it's own rules with the way it did this. All the promos say feature updates twice a year, and reversion is allowed to the previous version within 10 days if it doesn't work or otherwise isn't satisfactory. Yet, 20H2 was effectively done in 20H1, just flick the switch and the options published don't happen.
disgusted again