What happens is the blind person listens for traffic and when it sounds like the appropriate traffic is moving, s/he tells the dog to cross. The dog will simply disobey if it's unsafe. So it's the person that makes the decision to go, not the dog.
So in your situation, you let the person know that it was okay to give the command. What would have happened if you didn't say anything is the team would have waited until the person thought it was safe, and then she would have told the dog to go.
Don't worry; you just helped speed things up a bit. They would have been fine if you didn't help them, and they're fine now since you did.