During the artist search phase, I got some comments regarding the concerns of AI being used. While that's of course very difficult to 100% rule out, based on the interactions with Deniis and the resulting consistent adjustments to sketches, as well as the layered source files that he submitted for his completed work, I would say that it's safe to conclude that it's not the case.
I will be attaching the source files for the three test commissions here so those who have doubts can verify themselves that doing all those intermediate steps and layers would invalidate the whole use of AI image generation.