Shot VP9s almost exclusively from 2015 until earlier this year, to the tune of approximately 75,852 rounds, and habitually used my trigger finger to dump the magazine. Never an issue. I understand the concern about using the trigger finger for something other than pressing the trigger, but I've not experienced any issues in real life.
Pressing the paddle involves pushing down, not back.
The paddle is behind the trigger, not in front of it.
Excepting "tactical" reloads or administratively unloading the gun, the gun is usually empty (or has experienced a stoppage) when I am pressing the paddle. I'm generally not performing tac reloads or unloading under stress or at such speed that I'm going to fat-finger my way onto the trigger when I don't intend to.
Perhaps different hand sizes or levels of dexterity face challenges, and obviously @
GJM's anecdote shows that it
is possible, but it seems like a rare occurrence.
Granted, I'm also ok with using my trigger finger to activate a WML (again, sweeping down, not back)... I'm just not of the belief that my trigger finger can only be trusted to do one thing when there's a gun involved.