Don't know why he is available for grinding, but I can tell you he comes from the "Instigate Defection" assignment.
He is probably showing up for Rare grinding because his rank is set at LT. JR, where other purples are LT, I am not sure which part is incorrect though. The VR coloring, or the Rare rank. I figured someone might like to know.
Yeah Instigate would be where I got him I think.. that would explain bound.