I have a suspicion that the Royalty Free suppliers often encourage youtube. Many Royalty Free products require a one-off payment, so are NOT copyright free. I suspect they are trying to encourage people to buy it. If you have paid for royalty free material, you cannot share it with a colleague and then have them use it free in most cases. This I strongly suspect is what is happening. YTs own search system could be correctly identifying the ‘free’ music.
Unless the music producers keep their material to themselves, youtube will spot it. I’m using guesswork, but I wonder if youtube look for repeats of music – so when they find 6 or 7 videos with the same fingerprint, common sense would flag it as an infringement. Any form of repetition is what the automated systems will detect. The fact you have permission is for arguing later?
