I don't think anyone would defend buzzing close to pedestrians' heels as soon as they have cleared your lane, but if it is a large crossing, is there really a problem with slowly continuing once they are well clear of you - at least 2m - and still moving away from you?
I can't yell down from my moral high horse on this one, because I've done that myself. But the issue is not whether there's
'really a problem' with it.
There isn't
'really a problem' with remaining seated on a train when an elderly person has no seat. There isn't
'really a problem' with going through a door with a closer and letting it swing in the face of the person behind you.... Lots of people do both and it isn't
'really a problem'.
The thing is that it's discourteous or may appear so and the advantage gained by not waiting is trifling.
Yesterday a driver (also a cyclist, I'm guessing) waited behind me and my soon as we 'wound down' after a 10-mile piece of work. We were climbing a long hill, so this driver waited behind us at 9-ish mph for about 3/4 of a mile. I dropped back to give him a chance to pass us in two bites, but he just sat there.
In truth, he could have passed but it might have been a little close. When he did, I got a toot and a (nice) wave and I waved my thanks. Alongside that sort of courtesy (lovely but unexpected), waiting for 89-year-old Iris with her new hip to make it over a crossing is little to ask.
Just be lovely to everyone and the planet will seem a nicer place.