Well that's what I though as well. But the sportline doesn't have an sd6 version.
Also, I don't know the validity of THIS but mx5 and bt5 are the same from what I understand.
In addition to this, the sku #is referring to the metal version, which are from my understanding their high end series. http://www.icsbb.com/product/ics-02-mx5-sd6/
Anyway, I emailed them and waiting for an answer. I'll update when I get it.