Finger position for one thing. Of course it varies from shooter to shooter. Mine lands just low enough to get slapped by the stock trigger "fangs" but not by the fangs on my HBI.
The safety lever also sticks out slightly past the front surface of the trigger, and the trigger face is sort of "wedge" shaped. This concentrates more force on a small area and makes a trigger feel heavier than it is. Imagine if the trigger was as thin as a razor blade and you get the idea. Apparently non-US guns have a flatter trigger cross section, but US import laws require some guns to have a "target" trigger for "sporting" purposes, hence the wedge shape and serrations. Same reason Glock 19/26s have a serrated trigger instead of smooth like the G17.
Regarding your hypothesis on energy during shooting, you're right. The trigger action is the same as a Glock. While other guns simply have a spring that provides consistent forward pressure to return the trigger, the Glock/P10 works in reverse. As soon as the trigger releases the sear, the trigger spring keeps pulling the trigger rearward. The trigger weight at this point is zero. When the slide returns to battery, the striker leg catches on the trigger bar. This force pushes the trigger forward against the trigger finger. So your finger feels ~5# of force at the break, 0# after, and 5# again on reset. Depending on trigger finger timing, the trigger can literally "slap" your finger as it pushes forward. This is also why it's so easy to ride the reset on the Glock/P10 vs say an M&P or any other striker fired gun with a traditional sear/trigger return spring setup. To test this while dryfiring, lock the slide to the rear, lightly hold the trigger back, then release the slide. You'll feel the abrupt change in trigger force when it slams forward.
You can either change you grip/finger position (not likely due to body mechanics), of pickup an aftermarket trigger. Sanding my factory trigger to be more flush didn't really help in my case.
