This doesn’t seem that hard to test? Put a phone on WiFi, run it through a traffic sniffer, and see if it is constantly sending little audio packets to listener1486.facebook.com or whatever.
Or heck, open up a phone and stick a probe on the mic lead. See when it is getting power or not.
There are smarter ways to do this without constantly sending all the audio. Wakewords + surrounding snippets for example. In fact if the audio recognition is done on-device then only the text data could be sent which would be indistinguishable from telemetry.
Or heck, open up a phone and stick a probe on the mic lead. See when it is getting power or not.