butters yes, just found it (as MS Support didn't reply yet).
https://learn.microsoft.com/en-us/microsoft-365/security/defender-endpoint/device-control-policies?view=o365-worldwide&tabs=Removable
Scroll down to the little yellow warning, which should have been on each page of the documentation on top imo:
The https://learn.microsoft.com/en-us/microsoft-365/security/defender-endpoint/microsoft-defender-antivirus-updates?view=o365-worldwide#february-2024-engine-11240209--platform-418240207 release causes inconsistent results for device control customers who are using removable media policies with disk/device-level access only (masks that are less than or equal to 7). Enforcement might not work as expected. To mitigate this issue, rolling back to the previous version is recommended.