That's a problem of dealing with those video/camera/audio "superstores" like B&H or Adorama. For them it's just another item added to a catalog of thousands of other items. They are not a dedicated audio store, but I can guarantee you whenever a new Canon and Nikon camera is released - they will have it in stock right away.
Well, my 2 cents:
I've been buying all sorts of gear, both audio and photographic, from B&H for, literally, decades. B&H is the platinum standard for on-line, mail order and brick-and-mortar sales. They deal honestly, ethically and promptly -- if you check them out on www.resellerratings.com, you'll find that's true. As I understand it, all US product distribution for Fiio comes through Fiio's US manufacturer's rep, TekFX. This is a common scenario for smaller manufacturers like Fiio that don't maintain their own distribution network in other countries. B&H must get their Fiio stock from TekFX, just like every other authorized dealer in the US (including Headroom, from whom I ordered -- I would have gotten it from B&H but, by the time I decided I wanted an X5, B&H was no longer accepting pre-orders). Nikon and Canon, on the other hand, are large enough to have their own distribution network in the US and, because B&H sells such an enormous quantity of their products, I'm sure B&H is given special treatment. Note, too, that major audio companies, for example, Tascam, almost certainly have their own distribution networks and B&H would get product direct from them, too. It's not a question of whether its cameras or not, but whether the manufacturer does direct shipment or through a manufacturer's rep. Note that Headroom is a dedicated audio store, but they're not getting product any sooner than B&H.
I have no connection with B&H, other than I've been a very, very satisfied customer for decades, and know that they are extraordinarily customer-focused, and provide excellent, completely reliable service.