My rescue dog Radar has always been a bit cautions with new people. Once he gets to know you, he loves you, especially if you let him crawl into your lap. But he can be fearful around new people, so we have to be careful with introductions.
Introducing rescue dogs to new people is challenging when you don’t know anything about their past experiences with humans. Of course, every dog’s personality is different. But the rules of safe dog introductions apply to all types of dogs.