Apple USB Restriction

Apple USB Restriction

Hi,

Testing the MDM feature and have stumbled across a weird setting - 


I would like this setting on so that it is not allowed - but the only settings I seem to have are allowed - or User Controlled. Shouldn't this be a restrict setting? 
I'm trying to work out how to enable this across the profile so that we can ensure it isn't set. 
Is there any guidance on how this can be set? Does it need to be configured by apple configuration manager? 

All the devices are in our Apple Business Manager and synching through to MDM so i'm just trying to get my head round this to work out how we can get the device locked in that aspect? 

Any ideas would be appreciated!