grown up cherub

Andy Smillie just let me down.  I started reading “Flesh of Cretacia” and came to a line that really bothered me and I had to stop reading.  

“This was to be Hamield’s last mission before elevation to full battle-brother.  The veteran Scout already bore many of the marks of hs progenitor.  His once dark skin had paled, his eyes had the piercing blueness common within the Chapter and his close-cropped hair was streaked with blond.” (emphasis mine)

Okay, if blond Sanguinius is your Sanguinius, no prob.  There is more substantiation for that Sanguinius than dark-haired Sanguinius.  His eyes are also described as blue or amber, to about the same extent.

But why, WHY does Smillie have to put emphasis on white skin?  Baal and its moons are hot deserts.  Why could Sanguinius not have olive skin, like Rogal Dorn?  Why does someone with dark skin have to lighten to show his being more like, well, an angel?

I thought to the Ultramarines, who have a primarch who looks like a grown-up cherub with curly blond hair and blue eyes.  Yet there are black Ultramarines and dark-haired Ultramarines.  To have an actual angel be pale skinned as something he passes down to even his dark-skinned son just makes my skin crawl