On the cars with DuoSelect (that feature the paddles as standard), there are buttons on the back of the steering wheel too but they perform a different function. They aren't particularly easy to fathom either.
Not sure the buttons on the back of the steering wheel would work well as gear change selectors though - I would be surprised to learn that that was the case on an Auto car. Anyway, as I said earlier Elliott, you must go and drive the car. There is only one way to find out and that's by getting behind the wheel and trying the buttons out for yourself.
I always thought the 'triptronic' buttons on the front of the Porsche steering wheels were pretty horrible. I can't imagine gear selector buttons situated on the rear of a steering wheel being any better - likely to be worse quite frankly!
We have a sporty C class Merc in the famiy with AMG styling bits and it has these poxy little plastic paddles that are there for gear changes. Whilst they work a bit better than buttons they are still pretty naff in my opinion. No, .. if you want F1 style driving, it has to be the big fixed paddles behind the steering wheel that are attached to the dash (and don't move as the steering wheel is being rotated). On the DuoSelect and the GTS MC-Shift cars, the paddles are some of the best I have seen - they really do exude quality. There are lots of cheap bits used on our Mazzie's but the paddles are one notable exception.