I think they are BST because they used the mold of a european pump to make the body of these pumps rather than going through the large expense of getting an injection mold made specific to them. They look a lot like much cheaper pumps from the outside, but they're filled with Ecotech goodness inside, not the cheaper stuff.
I think it's great that they are making the adapters available. It's a little iffy to force on NPT with lots of tape and the adapters would otherwise be pretty difficult to source in this country for a reasonable price.