Observations. Look at the tail flicking in combination with disposition. Cats generally do not wag their tails if they are happy.

Have had cats for well over 40 years. Have had Vets tell me the same thing about Meowing. Turned out the cat meowing had a rare form of Cancer. Truth is my current trio of 5 year old kitties never made an utterance of any kind until I started playing YouTube videos of other cats about a years ago. My commentary is based on the way in which my cat reacted to this video. Thank you for asking rather than just down voting. Truly love our furry friends and want what's best for them and our relationship with them. In no way shape or form do I consider myself an expert. Just an observer.