I, too, am wondering why no cumulative update since:
2023-10 Cumulative Update for Windows 11 for arm64-based Systems (KB5031358) - installed 14/10/2023
The about box shows:
Edition Windows 11 Home
Version 21H2
Installed on 14/01/2022
OS build 22000.2538
Experience Windows Feature Experience Pack 1000.22001.1000.0
I get regular updates to Defender, etc - just nothing past 21H2
For reference, Parallels reports: Parallels Desktop for Mac (Pro Edition) Version 19.4.1 (54985)
And my M1 Pro MacBook Pro is running macOS Sonoma 14.6.1
TBH, it's not a great issue as I rarely use Windows nowadays - most times it's run is to get updates! It's there as a backup for a few programs I might need that don't have Mac equivalents (though that is probably now a luxury); I use my Ubuntu VM more and, even then, nothing show-stopping. I've run Parallels ever since switching from using a Windows PC to a Mac in 2012, at which time continuing to have ready access to Windows was essential. My annual licence is up for renewal next week and, whilst I'll probably let it auto renew this year, it might be the last time.