Not if you look at him playing dead straight on. That photo is still with his body angled back a bit, and the bass pointing more at us, the viewer. If you see Pino dead-on in the multitude of videos available on the net, his hand and arm rests at a natural, unforced angle on the body of the bass, or even floating off the body. He's not unnaturally bending his wrist, and is plucking while keeping his hand and forearm pretty much in the same line. I see the 'fingers are perpendicular' thing you're talking about, but there's still a bit of an angle BACK, plucking with a natural flow.
I mean, this video - even sitting - shows that he plucks with his hand angled a bit more back, without any extraneous bend in his wrist. It also helps to keep his hand ready for his palm muting technique we see so much as well.