Most TV sets should not normally need microphones, and if they have that in some models (as long as there are models without), then there should be a hardware switch to disable them. However, "continuously sweep home networks, map secondary devices, and log microphone audio while appearing to be turned off" is also stealing and wasting your power.
Every speaker is also a microphone
Speakers can act as part of a useful microphone circuit but you're missing all the amplifiers and ADCs and other stuff to use it as one in any sane speaker driver circuit. They'd have to intentionally add all that, which maybe they would, but it'd be easier to just stick a tiny $0.05 all in one microphone chip on there.
The NSA enters the chat