Never heard, nor seen the chatter jaw. Interesting.
Miko lifts his leg to pee. When I got Koji, strangely enough, he never did it. Koji does a squat. Not like a girl squat, but where he lowers his back end a bit straight down (not curled under like a girl or if he has to poop). No clue where he learned that. He still does that, 6 years later.
However, both my boys are neutered and neither mark.
I recall a thread about this. It seems as though it's random. Not always learned. Sometimes it's a dominance thing. I remember one person saying when the more dominant dog passed, the dog who used to squat, now lifted his leg. I have no clue.
One suggestion is to cut the hair around his privates. That's what I did. Trim the fur above, so when he'd go, it wouldn't hit that hair. OR I'd let the fur ON his privates grow long, so that when he'd go, it'd dribble down that....to the ground, instead of straight forward, onto his tummy area.