TV shows are completed and in the can well before air date. It is entirely plausible that the interested party in having the content identifiable by Shazam like services submit whatever needs to be submitted for new content
That can't recognize what you say. But, it can ID where you are in a specific show out of zillions of hours of shows.
A quick search for “audio steganography” should answer your question (and be a fun rabbit hole if you find that sort of topic interesting)
Streaming services watermark the video as opposed to the audio as I understand it.
But that's for tracing pirated content back to the originating user account. It's not particularly useful (also entirely unnecessary and overly complicated) if your goal is to ID a piece of content as opposed to an account.