Let me add that downshifting this way is not subject to the 6 sec mandatory manual interval you get if you downshift with the paddles.
This has its pros and cons. If you downshift to floor it (for passing another car, or because you remembered you need some coffee) it is great, you punch briefly the pedal about an inch and you get one downshift, you punch it two inches and you get two or more gears down (you need some experience on how much to punch, NOT pedal to the metal). Then you can feed it gas as you see appropriate, and the PDK will do its job as it sees appropriate.
The con is when you downshift by punching 2 inches for braking. It is very counterintuitive and man, oh man, it can scare civilians, women and children.