I can’t speak to how LG does this now but I ran an agency that built Smart TV apps and built one of the first ACR powered apps on LG about 10 years ago. We were working with a company called “Cognitive Networks” which later was bought by Vizio and is now their Inscape product. At that time one use case wasn’t just tracking but actual interactive “sync to broadcast” apps (you can still do this, no one does, and I don’t know why)

At that time during testing Cognitive could literally see what we were playing on our TV (not full video but the frames used for fingerprinting)

They don’t use Cognitive anymore for obvious reasons and there are several audio based ACR solutions but they always had issues with sections of video without much audio to work off of so we’re always considered inferior. They are fine for usage data however.

Anyway my $0.02