You people are quick to label OP things without knowing where his doubts came from, don't arguewhen you haven't been in the industry.
Who's more arrogant, OP asking for proofs or the ones with zero experience in the field attacking him on things they have little knowledge about?
AI things aside, this is a prime example on how non-artist shouldnt kepo on things they know nothing about.
OP brings a valid concern. There are some unusual artifacts in the picture and for people who took the time to learn Digital painting it's relatively easy to pinpoint.
The drawings are great but the sketches/concepts the artist' son gives are only a fraction of the pipeline. Comparing it with the final render proves so little. Matter fact it brings me more questions