My first readings about it were from the Canadians about maybe 5-6 years ago.
They tend to vaporize OA because of temperature concerns (drizzles would dampen the cluster).
It wasn't much after, maybe a year, that OA drizzles seemed to become trendy in the US.
I think that it was because US beeks were lazy and didn't want to seal up the hive to contan the vapor, etc, etc.
I think you've talked with Dan Williamson before, he used to do OA vapor, (not sure if he does now still or not).
(Heck, he might even be the one that got you started on this topic?)
It never fell into favor with me. The acid is still a low level poisoning to the bees. It's been show that high acid diets adversely effect larvae to forge time, and overall forge life of bees, so I'd assume OA does the same if it acidifies the bee's hemolyphic system.