After you use the "paddle" for one downshift, what happens if you use the paddle again to downshift again, say down from 4 to 3 and another paddle down to 2?
The CVT in the Citroen is set up completely different from the Subaru, same basic system but a whole lot different designs and operation. So, you really can't compare them.
The "electronic" brain of the Subaru is simulating these shifts and moving the CVT belts to the correct preprogrammed ratios. When you use the paddles you override the auto system as programmed and you take control of the shifting. The paddle should allow more downshifts and it is up to the driver to find the right gear for the situation at that point.