I noticed those last week too. Its a very curious item - a 12-port expander seems like a strange thing to even build.
Unless I misunderstand, it takes 1x 4-port 8087 in and gives 2x 4-port 8087 out, so its really only a net gain of 4 ports. Of course I guess if you have a 12-drive chassis it could be quite useful - but you can get a 2nd M1015 for almost the same price and have 16 ports net.