I'm pretty sure by north-south they are talking about the direction the panel lies in, i.e. the faces point east/west.

But even under your interpretation, you aren't always right. If you're far-ish north of the equator you want south facing panels (and the reverse) and if the cells are cheap enough it makes sense for those panels to be bifacial, with one side permanently facing away from the sun, to get a bit of extra energy from ambient light. Especially in winter when there is less sun (so energy is at a premium), and highly reflective snow resulting in a lot of ambient light.

what if you're in the southern hemisphere?

I’m pretty sure they mean that the width of the panel is north-south so faces are due east or west