Intune Policies for Microsoft 365 apps not updating web apps language for all users

[KK20]

This is an odd one.  I have a Policies for Microsoft 365 apps policy for all users, it sets the editing language for office as UK and enables the UK language.  This does not seem to reflect for the majority of users, most users are on US for office.  Outlook (and Outlook new desktop app) seem to be set as US, but the odd thing is that some documents in Word are UK and some US for proofing!  The setting can be changed via cog->general->language time.  PCs themselves are set as "windows display language" English UK, region is English UK, keyboard is English UK.

 

I cannot seem to nail down how to set everyone as UK for proofing/editing for "office for the web" and Outlook New desktop.   For the machines that use desktop 365 apps, the GPOs work just fine for UK proofing.