they cleaned the cvt filter with fuel and re fitted it.
probably also just filled in a 4 litre cvt oil and didnt care about how much came out and how much to be filled back in.
however as per my experience they do the same in vitz cvt and there have not been any issues with this simple procedure to follow.
my take would be to religiously follow 40k change interval with this approach since it doesnt ensure complete cvt oil change so some old and new cvt oil gets mixed anyways transmission should be fine as long as u r not dragging the change interval beyond 40k kms.