Ok, this comes down to the same problem that I had with other groom settings.
The pictures above were done with the Binding Type set to Skinning.
Now, when I set the binding type to rigid, the problem disappears, as you can see in this comparison:
Binding Type Skinning:
Binding Type Rigid:
Both pictures were taken at the same frame in the same sequence.
@Charles, as you were interested in this type of bug in another thread of mine, would you be interested in this project to have a look into? I can zip it up for you and upload it somewhere.
r.Hairstrands.SwapType is set to 3.