@konato I was asked that by a friend as well actually. Most will have it on the side, for exactly the reason shown.
Though for this one this seems wrong. I put the label towards the back where it should be. Putting the slit to the side here would put the seams to the front and the back, which looks odd. I dunno. I don't have many pencil skirts anyway.
3 of them. This one. A red/black one with no slit and a green/blue one with a slid on the side.
If one wears the skirt at the appropriate length (not like me faking a mini-skirt) it looks fine.
So: TL:DR I have no clue.
Maybe
@guyinaskirt has an idea here