I'm not sure. I just checked the user manual and the only thing it says is: "The magazine release lever can be pressed with the thumb or index finger of the firing hand, in most cases without adjusting the firing grip."
I'll agree with the manual statement except for the part about "without adjusting the firing grip".
I like my HK P30SK's that I'm learning to adapt to the paddle magazine release. Frequently, I use a finger on my off hand, sometimes I use my trigger finger. The strong hand thumb just does not work for me. I guess my thumb is not long enough.