In another thread about the reveal of the poster, I had mentioned that I think the five heads were 3D scans of the actors. And being that this video does not mention that at all, I assume they must not have been 3D scans after all. If they had 3D scanned the actors, they likely would have included a quick BTS clip of that session in this video, or showing the 3D scan being imported into Blender. That would have gone a long way in helping to prove that it wasn't AI-generated. Based on what we do see here, I assume they must have just sculpted the models from scratch in Blender.

But with that said, maybe they did start off with 3D scanning and just didn't think to record the 3D scanning session. Everything in this video is just showing off the final product in Blender/Photoshop. It's not like we are seeing a timelapse of it being created or something. They were not necessarily prepared for all this backlash and the need to have documented the whole process.