No probably not, but for me, it's the first sign that the dog might be a biter.Unfortunately, that happens a lot in most dog parks. Lots of people, who have no business bringing their dogs, bring them anyway, with sometimes disastrous results. But I don't really think that a pulling dog is always going to be aggressive.
I make my dogs walk BESIDE me on sidewalks and pavement, on the way to our destination (usually an open field). Once we get there, I use a cue word to release them and then they're allowed the full extent of the leash, as long as they're not pulling.