I think it depends on who you listen to. Some feel there's no need for your dog to play with other dogs. So they'd go around other dogs and engage with their pup to teach them they're just furniture.
As far as reactivity. As far as I understand, that comes from having bad experience with dogs. So for example, a dog was exposed to another dog and the other dog spooked your pup somehow.
If your pup has good nerves then it shouldn't affect him but if he doesn't - it might.
All my experience and some stuff I read. I might be wrong.