Definitions vary from state to state, but it's common for the legal definition of assault to require both willfulness and the knowledge that application of force will arise from your actions. You seem to think that bar has been reached by nonverbal cues. It might have been. It's different from just unwanted touching (indeed, often not actually requiring contact). Legal definitions aside, "assault" in popular language is also not just unwanted touching.

What your story does show is negligence causing injury. That's still bad. Nobody's condoning that.

That all said, I don't have a dog in this fight so to speak. Best of luck.