Thanks very much for explaining, @jdstrand
I realise it’s tricky to document these interfaces when there are differences between implementations, but I’ve added comments on the Supported Interfaces and pulseaudio pages to suggest making this more clear in the documentation.
It also wasn’t obvious to me that I needed to install the pulseaudio snap (and stage the libpulse0 package) for this interface to work on Ubuntu Core.
(I would edit the documentation myself, but I’m not sure what the policy is on documenting differences between implementations as I guess the documentation is supposed to apply to all distros, not just Ubuntu)
Thanks