I thought that @Odysseus_of_Domntr was right. But actually I noticed something very peculiar. I combined first "human pet" and then "petplay" with tags like "public use" and "slave". And what I noticed is actually pointing towards the OP being right. Basically both have the same percentage of "public use" and "slave". Now I actually agree that it should be as Odysseus says, but that doesn't seem to be the case. Another interesting thing is that there's no single work with both "human pet" and "petplay" which really does make it seem like at some point they changed the word. (technically now there's a work like that, but the tag has been added by the community) so, unless some hentai historian can explain it, I think we should actually merge the tag. A new tag for non consensual dynamics might not even be needed since you often just need to add "rape", "humiliation" or similar tags

I agree with below comment.

No, pet play implies the dynamic is consensual, the human pet is closer to a slave-master dynamic, which is not consensual, usually.