I asked CS at BBTS about this and recieved this canned (but polite) response...
With regards to new product offerings, we typically have to await an official solicit from the manufacturer in order to offer an item on our website. The major brands are almost always offered so it is just a matter of time before you might see those listings. We try to carry as many products as possible, and new merchandise is constantly being published on our website each day. If you have not already, we recommend signing up for our newsletter, as well as following our social media pages for the most current updates. We can be found on Facebook, Twitter, and Instagram which post the newest arrivals and upcoming pre-orders.
Since it's a well-known fact that Sideshow controls the HT distribution in the US, they may be the ones holding it back presumably to up sales on their own platform. I like ordering from BBTS - the customer service has been stellar and even though there is a bit of a wait from them after a figure hits, they always double-box and for me, they are closer (midwest) so ship time is less.
Time will tell. My concern is that BBTS is only allotted a low number and they PO goes up and,in a flashback of the old days at SSC, is closed within minutes of going up, leaving a lot of folks in the cold.