No, it's not. We can use facial recognition, we can use voice signatures. It doesn't even have to be recorded, as the device setup can record those signatures of consenting users and refuse to transmit or save any data that does not match those signatures.

Tell me, which of these do Alexa and the like perform?

Would it be more difficult? Yes! This is the reality for any company where rights and laws actually matter. If you can't abide, you can't release. Very simple.