Very, very good highlight! They did both the fans and the concept itself a disservice by introducing it through a hand-wavey half a paragraph’s worth of retcon…

But that just tracks with James Borkshop’s slew of highly questionable decisions as of late. Imagine how much new blood (and fresh cash) they would’ve drawn in with a proper expansion to the story which would open up augmentation to basically anyone. How hard is it to attribute it as a modification of the process made by Cawl, who’s already at near Mary-Sue levels of big-brainedness? And it’d add more flavour to Guilliman’s rather rational take on doing things as well! Plus it’d reinforce the long-term tragedy of the entire universe itself, that everything is doomed even when Humanity’s not being as big of a bunch of regressive zealots because we already made things bad beyond the point of resolution. Poignant message, imho…