This is not as extraordinary as it seems. Cats often respond to a hand being outstretched by touching it with their paw. My cat does it so I should know.
I called it a sign of affection which I still think it is. It is probably domestic cats learning human mannerisms or adapting to the human environment. Humans like to hold hands and touch. Depending on the cat they can have similar likes. Actually you also see it between cats and cats touching dogs.
|Photo by DW. The cat is Marvin and the dog is Daisy.|