I don't believe this to be true at all. I did an observational jump seat the other day (on a mainline carrier,) and the captain summed it up pefectly. He said "Your first sentence when talking to the captain about the jumpseat should always end in a question mark." This wasn't directed at me, but at a jumpseater he'd had the previous day. The fellow showed up, hadn't shaved, and stated "I'm riding your jumpseat." The captain rebuked him for not asking (rightfully so, IMHO,) and asked the kid to run a razor across his face before boarding the aircraft. The guy got all huffy, and dissapeared.
So I think most major guys are a little more rigorous when it comes to getting on the jumpseat - and rightfully so. I've also noticed that most of them are just as respectful when they came to ask for a ride on my jumpseat. Many aren't as formal as to fully inspect all of your documents, and I think every captain has been in a situation where he's so burried under things that he just waves the guy on to the back. Many at the majors are unfortunately unaware of what is going on at the regional levels as well. But I think most major captains will definately give you the boot if you do not show propper respect and courtesy.
And from a former 'skier - XJ rocks!