Hi Fraser. I understand your logic but unfortunately don't think it is correct hypothesis.
Yes, multiple IPv6 addresses are being assigned (as is the case with most devices on the network) but only one MAC address. I've checked and the MAC address listed in the DUMAOS app matches the MAC address of the device.
The Google Home is an old device and has quite simple network functionality / configuration. It certainly doesn't support Random/Private MAC addresses.
If it did, then it should show up as multiple devices in the app (one online and the rest offline), each time a new MAC address is generated, which is the case for the iPhones that connect to the router.
In fact, as a side issue, that is one of my pet peeves, the Offline Devices get filled with multiple entries (for devices that have Random/Private MAC addresses enabled) and these redundant multiple entries have to be cleaned up manually, one by one! When will bulk select and delete functionality be available (is it on the roadmap or perhaps already included with the latest build)?
Also, the Google Home is only connecting via 5GHZ. When it is blocked, it doesn't alternatively try to connect via 2.4GHZ. I've tested and monitored this to confirm. The 5GHZ and 2.4GHZ bandwidths are already combined as a single SSID.
The Google Home is actually his alarm clock, so I don't really want to have to physically remove it every night (especially when I should simply be able to block Interest access at the router)!
Any other ideas (or can this be escalated to the dev team for comment), as it definitely seems to be a glitch.