Happy to say it's NOT common, but much depends on what risks & what precautions you take. Obviously I can't comment on specific circumstances in a video
that I haven't seen, but IBD has to come from somewhere. It's not thought to lie dormant for "years" in a boa before making them sick, but it's possible that it
was transmitted to that boa from handling other people's snakes, or perhaps by sharing snake mites (also thought to be vectors of diseases like IBD) that could
have "hitched a ride" from a pet store or from an "expo" (where it seems there's always some vendor selling snakes that have mites, & when people handle them
to possibly buy them, the mites can be transferred via clothing to other snakes). So anytime you're exposed to other snakes of questionable health status, you
can help protect your own snake by not going near your own snake at home until you've showered well & changed clothes.
What makes IBD so awful (besides the symptoms & bad outcome) is the lack of available treatment, but it's not the only contagious & fatal disease that snakes
can catch. I suspect that many such fatalities have been wrongly attributed to IBD, and unless tests were done, it's just a guess, not a certainty. But for sure,
it's a concern...it's just not thought to be "common".