Jackson unfortunately is not. He's not... mean at all. He just doesn't love everybody or feel a need to get very close lol. The most he does is sniff a new visitor and take a treat possibly. Otherwise he prefers no touch, no talk, no eye contact
Now with people that he knows, once he loves you, he'll love you forever. Most of my family -- aunts, uncles, grandparents, parents, etc, he greets with much enthusiasm.
Most yorkies I meet are honestly pretty friendly with strangers.