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I wouldn't be surprised if they can't tell the difference between a person and pet. Also wouldn't be surprised if they used that data to push pet food ads at you somewhere or just sold that info to a data broker.

IIRC most motion-sensing home devices are tuned to ignore pets, as best as they are able. They don't get it right 100% of the time though.

How does having a dog or cat make this less useful? It detects motion, and it can still do that with pets.

I'm assuming you really meant "detect human motion", which I don't think is a solvable problem at this point in time, at least with high accuracy.