I'd guess that this research was done by someone who is not familiar with the normal vocal repertoire of a domestic cat.
The vocalised purr is a normal greeting between a Mother and her kittens. In a social situation it is used between adult cats and fellow members of their "family" group.
The reason cats and humans can enjoy one another's company is that feline social signals nearly make sense to humans, and human social signals nearly make sense to cats.
A human greets a cat by saying "hello" and offering a stroke.
A cat greets a human by giving the greeting due to a group member, and offering physical contact.
If this is manipulative, then so is every normal greeting.
You'd have to be an extreme individualist to believe that social interaction, or good manners, to put it in a human context, are mainly for the purpose of solicitation of favours.
Felicitation would be a better word.
Cheers
Dave