I think what they're doing at 5:50 is trying to give the impression of roughly hewn metal with a bump texture file. It may be in the properties of the model. Though it's much smoother on my PC, very effective. Not "pixelated" as here. I have an Nvidia 1080ti card. I see this effect on VW and BMG locos, too. This is a great model. With luck, they'll morph it into the very similar 1366 for the forthcoming Dorset Coast route. Here's hoping!