You're right, I read this one too quickly. Pleater has posted before about doing this to top apron pleat, which is where it doesn't work too well (in my experience). Doing this at underapron works OK as long as, on a machine-sewn kilt, you haven't already topstitched apron edges.

All in all, I prefer Barb's hemming method to the "raise the pleat edge at top" method. More controllable results.