For what it's worth, I've seen these sort of dogs go either way as far as actual aggression, though I know that doesn't help ease your concerns when it's your dog they're greeting. I always cringe when I see dogs doing that sort of "greeting" in the lobby at my work, but more often than not, if the other dog is of a "friendly" sort, it's no problem. Now, if the other dog is also an excited/tense greeter, that can spell trouble.the other dog stood there with a pin straight tail and it's hackles starting to show
It's a pain when people have no idea their dog is being a nuisance, and even more so when they can see it but just don't care. That's why we mostly avoid public areas/daylight hours for our exercise/training times, but sometimes you can't avoid it!