The point was not so much about braking distances (although there must be road conditions where those are acceptable for a bike) but about the distance travelled before the actual braking.
3 m difference between 20 and 30 mph means you are just that much closer to the obstacle. So having a biker that first wonders if he can keep the bike upright at 20mph then says that avoidance at 30mph would be easier was a bit… surprising.