Guess he never heard of passing on the left? Why did he stuff himself into that position in the first place? Sheesh. As the doc says, unlikely you'd go down though. We had that happen on a club ride last year, the rider in back went down, the front one did not.
Last week at our club meeting, we had a coach speaking. One of the things he brought up is bike handling he teaches, including wheel bumping drills (performed while riding on grass). Says that you can recover from it, but if you're not trained and practiced in how to react, you go down. Interesting idea.