I just get a classic mental picture hearing the description of a flock of women scattering upon approach. Seen it happen with a group of "speed-walkers" that were in their own world. Like 10 of them. Can only imagine what the road outside the school their prodigy go to every weekday looks like in the morning and afternoon!
Find that just saying hello is enough. Say it clearly with a bit of distance and let the rider(s) settle out before passing. Have been startled myself when the speedster comes up barking commands when passing. Is it discourteous? Guess so, but then I understand that they are in their "zone" and changing pace is a little different when you are cruising at 25 mph.