It is certainly a niche part of the market, and one category that still has quite a bit of room left for innovation. Despite the push for multipurpose gear and lighter base weights in the UL community they still don't seem to hold much market share.
I'm also very interested in the origins of things. Even focused on the relatively young outdoor gear market, this is seldom an interest that I can exercise with any certainty, but in this case I might have caught a break:
I think it safe to say for the moment that this is the oldest example of a modern sleeping bag with arm and leg openings, so for now at least I'm declaring it the first true mobility bag.