I went back to that thread and checked. He even refers to them wearing knee-pads in the comment. In your pic there are no knee-pads.
Right, I think that they're probably the same uniforms. When they're sitting down, they're hiked up. When they're standing up, you can see that they hit barely above the knee AND they are wearing kneepads. With the kneepads on, I would say that they are not immodest at all.
I've actually seen women wear these somewhat shorter skirts ... several inches above the knee, but then these relatively-thick leggings come down below the knee underneath the skirts ... to the point that it does not appear immodest at all to me.