There is no contradiction, in Guilliman's mind, between this offer and his brief flirtation earlier with the idea of killing Beta. They are both his right. Generosity and justice just happen to be more pleasing to him -- and how fortunate that at least one of the Emperor's monsters was raised with the concept of noblesse oblige!

"I have acted as I would with the leadership of a feudal world. How far the Imperium extends, and that I am Lord Regent and Lord Commander. I have spoken some of my Father, and brothers, and my sons. Few details of the government." He smiles slightly. "Of most agencies, nothing at all."