Erin, I do think it sounds like normal puppy behavior. I wouldn't worry so much about reactivity at this age (though of course it's something all puppy parents -- all dog owners, really -- should stay aware of and on top of). Bailey was like Jonah -- he would literally scream at puppy class (it was pre-K, basically, before puppy kindergarten, so they puppies were all under 4 mos.), because he wanted to play with the dogs and didn't want to "learn." As an adult (he's almost 3 now) he likes other dogs (he goes to daycare on weekdays) and understands dog behavior well -- and he also likes me a lot more, and has good focus and loves training. In his classes, we used him several times as a "barrier" between other dogs who were having a hard time focusing because they wanted to greet each other and play. I don't profess to be an expert, and am far from it, but I'm just posting to say that I really wouldn't worry to much about this turning into something or indicating something about future reactivity.
As to the rest of the discussion, I agree that it is important that dogs learn dog behavior. Maybe it's because I live in the middle of a city, but dogs here interact with other dogs on a daily basis, and I think a dog being able to understand another dog's body language is quite important. For example, we share a yard with a pitbull adult who I think was really undersocialized with other dogs. I can understand why his owner might have thought that was the responsible thing to do given his breed (she's really careful with him, which is great), but, honestly, he is awkward and kind of rude with Bailey. Not at all aggressive. Bailey doesn't really care about the behavior (he puts up with lots of rude behavior, and above being Mr Snarkyface himself, ha ha), but I do wonder if more puppy socialization would have been helpful for NeighborDog. At the end of the day, NeighborDog is a great dog, is (as one would expect of a pitbull) wonderful with people, and has a great life, so it's not a big deal. *I* just prefer to have dogs that are well-socialized and understand dog behavior, to the extent possible, understanding that dogs have natural inclinations one way or another.