Low yardage box pleat vs higher yardage knife pleats

[Steelkilt]

When you say billow vs swish, is that to say that the pleats tend to fly up more with box pleats, potentially exposing one’s rear?

Yes, it does look very different from the rear and it moves differently. A low-yardage box-pleat will "billow" rather than "swish", in my experience. Due to the shallowness and style of the pleats, it just doesn't have the freedom to move as much. It's apples and oranges between the two.

For one, the pleats are much wider. They tend to look more square and symmetrical than a one-way narrow pleating style like knife pleats in a high-yardage kilt.

One major difference I've noticed is that a box-pleated kilt tends to open up the pleats with minor movement, exposing the tartan inside the pleats more easily than a knife-pleated kilt does. This is because they expand out like an accordion (for lack of a better comparison). And again, the shallowness of the pleats pulls the material more easily open.

A couple of photos of the rear of my box-pleated kilt for reference: