For about 2 seconds, I thought this could've been Brad Cardoza, between the bald head and the massive weights used.
I would only call that bad form if he walked in and said "Hey guys, I'm going to do some strict curls for my bis and forearms." If he was intentionally powering the weight up from rep #1, then he's pretty much spot-on for technique. Curling 65% bodyweight per hand is rarely going to look pretty.
Also, something like that wouldn't exactly be for explosive strength (though that's certainly a side effect). He's turned an otherwise-isolation movement into a full body exercise. Again, if it was on purpose and goal-oriented, then it's not a bad idea.
If I were to do a movement like that, I probably wouldn't bother to use 2 DBs. I'd go one arm at a time, and I'd bring the DB a bit lower, to mid-thigh height.
If it matters, Charles Staley has recommended Power Hammer Curls for total body strength before, as has Mike Mahler. I'm also pretty sure Dan John wouldn't mind them much either.