It looks like M365 Apps for macOS aren't supported by M365 Apps for Enterprise device-based licensing.
This is causing us a headache because we have a small population of Macs but an environment where a 3rd party tenant is used for day-to-day working in our schools. This 3rd party tenant does not supply M365 Apps licenses for professional use. So, our own tenant just supplies licensing. This works well for Windows 10/11 endpoints using M365 Apps, which accept the device-based licensing. Because of our setup, we don't configure user-based licensing for M365 Apps as the users generally don't use their accounts within our tenant.
The solution would seem to be that macOS M365 Apps support device-based licensing. We could even cope with this requiring the Macs to be managed by MEM/Intune, as this is what we already do. The Macs are joined to the on-premises domain and synced to AAD.