Of course you're free to do what you wish, and even if the derailleur is 100% Shimano, you're free to return it since it doesn't conform to the published spec. Or simply because you're not happy with it.

However, you'll eventually learn that you shouldn't draw too many inferences from what corporate spokes people don't say. They choose their words carefully, saying as little as necessary to meet their needs, and leaving unsaid as much as possible.

OTOH there are countless possibilities, including that the derailleur was sold, and returned. the original pulleys showed some age, so they cleaned it up and installed new pulleys.

In any case, you came to the forum for help, and apparently are unhappy with some of the answers. But keep in mind that nobody has any agenda except to offer you the help you asked for, even if they don't offer it in the way you hoped.

So feel free to do what you will with the RD, but try to accept FREE help more graciously, even if you don't think it's that helpful.