You can research the specialized limbs on a simple research bench. Its not a "bug" but I think this cant be intentionnal. I mean, its spacer tech level, you need microelectronics, and you need a rare techprint.
That is the advance of the techprint.
And you never can complete the research with only the techprint, you only get 50% of the remaining researchpoints.
I assumed you will need a hi-tech bench to complete it