Without getting into the validity of the gp’s post, RenTec does seem to recruit from NSA/CCR, particularly in the early days. Again, not saying this lends credence to the gp’s post, just adding an interesting bit of info.
RenTech recruited from NSA early on mostly due to Jim Simons' connections there. The recruiting they do nowadays is mostly because there are some excellent mathematicians, statisticians, information theorists, etc. there.
I have no doubt RenTech has some of the brightest out there. However, any consistently high-performing funds warrant suspicion, especially considering how many hedge funds engage in questionable activities (corporate espionage under the guise of "forensics", hacking, insider trading). Showtime's Billions isn't as far off from reality as people think.
A perfectly innocuous connection could be that intelligence community folks are good at ... drawing conclusions from intelligence? It makes sense to recruit spooks to analyze and interpret mounds of proprietary but legally-gathered intelligence then.