Small correction: there is no Blacktron in those books. Blacktron wasn't even a thing yet. The bad guys are just generic black-suited spacemen.
Yes they aren't, but they're the predecessor. Frank Madisen (if i spelled that right) came up with the idea of Kazak's Army, and my guess is LEGO got on the bandwagon and made a theme for it, Blacktron. This makes sense, because if you look at The Unknown Galaxy the vehicles look just like Blacktron vehicles. (as well as the colorscheme)
Apologies in advance for going off-topic, but I just want to point out that unless an official source confirms the theorized link between Kazak and his troops in Jim Spaceborn: The Unknown Galaxy and the initial series of Blacktron, it remains merely that, a theory.