Not sure why they wouldn't continue with their Jet-II range, that's a good question for Flavio.
I think they called it a backup light simply because it is smaller than the Jet-IIIs.
To be honest, I think Jetbeam is probably a smaller company than we think it is, and probably don't supply it to any big organisations. So i think most of their customers are the general public which may include some, but relatively few LEOs. So most prefer rechargeable batteries or something that's abundant.
And from experience, CR123 are expensive and there aren't any cheap and reliable RCR123/16340 sources, that may be why they're not selling Jet-IIs anymore as they're harder to sell.
Since a 'backup' light has to be small, it'll either be 1xCR123 or 1xAA, since 1xCR123 is out, now only 1xAA is in the equation therefore we see what we see right now?
Please note that, i haven't asked Jetbeam anything, so this is just a hypothesis, don't kill me if im wrong, lol