The point is that it did no good to pass the cyclist if they arrived at the intersection after you and then had enough time before the light changed to gingerly pedal to be in front of you. Even if your top speeds were wildly different, the fact that you both still ended up in the same place at the same time but further down the road, implies that there was no need to pass.

To belabor the point, you would be said to have the same mean velocity, but different peak velocities.

I'm guessing if they didn't have to wait patently to get past a slow bike, they would have gotten through the intersection long before the bike got there. The only reason the bike was able to get back in front was because it delayed them earlier.

No, no it can't. But as far as I'm aware, the bike is allowed to ride in the 2-foot-wide gap. And still, the bike isn't stopping you from going forward. In the case when there really isn't enough space to pass the bike - the road is just too thin, the guy on the bike is a dumb asshole and shouldn't ride on that road.