Build 21277 is out as an Optional Update

Ok, here, chew on this...  I hadn't looked at this confusion for a while, but it, now, fits with the discussion... remember my saying with Insider Builds the blur was no longer AND I'd not made any changes? Well...

I just checked:

20H2, yes, I do have that set to Enabled & hence no blur.  So long ago I'd forgotten about it.

BUT❗

The Insider Build, which IS NOT blurred nor has it been for quite some time, is set to Not configured❗  In other words, it should be blurry, but it is not.

Decided not needed to put snips to show (or prove) what I'm telling you.

Cheers,

Drew

@Drew1903, @Johnny55, 

I don't think it is that simple, with my Build 21277.1 I see that my logon screen is blurred when I set the Policy "Show Clear Logon Background" to not configured, but I can change the registry entry  Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\System

"DisableAcrylicBackgroundOnLogon" and eliminate the Acrylic effect without configuring the Policy.

Then if I change the policy again to Enable and apply and then back to Not Configured the registry entry Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\System gets wiped out so that the behavior is the same as the 20H2 builds.

Perhaps you should check both the Policy and the Registry settings on your insider Build.

The Registry may have been set independently from the Policy. 

I remember when they first changed this and it was only working partially and not on all logon screens, so that I had to enable the policy to get it to work correctly. 

I tried the same sequence described above in 20H2 and it behaves the same way as 21277.

Ok, here, chew on this...  I hadn't looked at this confusion for a while, but it, now, fits with the discussion... remember my saying with Insider Builds the blur was no longer AND I'd not made any changes? Well...

I just checked:

20H2, yes, I do have that set to Enabled & hence no blur.  So long ago I'd forgotten about it.

BUT❗

The Insider Build, which IS NOT blurred nor has it been for quite some time, is set to Not configured❗  In other words, it should be blurry, but it is not.

Decided not needed to put snips to show (or prove) what I'm telling you.

Cheers,

Drew