[inferiorhuman]

Out of curiosity how is one of two stick shakers activated obvious when each is connected to a different person?

Stick shakers are noisy, but I suppose you would also ask and cross check the instruments. If only one stick shaker goes off you'll probably get various "something disagrees" lights going off, which should prompt you to check. Take this for instance:

https://aviationweek.com/awin/boeing-addresses-pitot-tube-an...