Only the last two Insider installs have had this occur on the login screen, but the settings are set the same as my public release with regedit and gpedit so not sure where to look now that governs that effect.
All my installs are W10 Pro.
@BryceSor,
My installs are also all Win10 Pro x64.
Hyper-V is the variable causing the different behavior with Insider Build 21277.1000 (or 20279.1) which seems to ignore the policy settings and always shows clear logon background.
Time for MS developers to explain why ? 😉
Edit:
Yet if I install a 20H2 Build 19042.685 as a VM guest with Hyper-V the behavior follows the settings and the logon background is blurred by default as it is normally on a real machine.
So the Hyper-V seems to affect only the behavior of the Insider Development builds like, in this case, 21227.1000 or 20279.1, while 19042.685 in an Hyper-V VM guest behaves correctly according to the policy settings. See the 2 pictures below:
Blurred picture on an Hyper-V Virtual machine with Build 19042.685 with policy "Show clear logon background" Not Configured

Same Hyper-V VM guest 19042.685 with Policy "Show clear logon background" enabled:
