Fellow biker here, and I think you're just stating an arbitrary line.

The first negligent action could be climbing on the bike.

I think I'm safer slowing and rolling through a stop sign in my truck than I am getting on the bike in the first place.

I realize it's different-- causing a threat for others and all. But I think the point stands-- you're just debating where negligence starts.

I tend to agree with the GP. It's an accident anytime it wasn't intentional, even if it's a preventable accident.