I had that problem too. It actually prevented me from enabling the new Advanced Data Protection feature which required all devices to be updated to 16.2, including HomePods. I don’t know which is showing the correct OS version but the only way I was able to get the iCloud device list to update was to factory reset the HomePod(s) in question.Under my iCloud devices, it still shows as 16.0.
This problem is now persisting with the past few updates and it’s annoying.