Every car I've ever worked on with calipers has slide out pads just like that...
> as the caliper still has to be removed during a brake change to pull off the rotor
Although pad changes are much more frequent than rotor changes, so it makes sense.
Even if you don't replace the rotor, you still have to remove have it turned (grinding the contact surfaces flat again), so the new pads make good contact, instead of being pressed against the ridges and valleys left in the rotor from the worn-out pad.
It just seems like a bit of over-engineering.
On a regular car you might have to have your rotors turned, but on something like this the rotors are more heavy duty and I think resist warping. Plus, on something like this you could run a lot softer pad (for track days) and need to change them out after a single weekend of use. It is still a good idea to sand the rotor surface, by hand, just so the pads will seat correctly.
Edit: And I do agree, I've never seen a "normal" car with the slide out pads... although they always look like you can do that until you get close and realize it is going to be a little more work than you thought. :)