On the video, I saw him use a mask for his chrome before he printed.
Masking isn't unusual for any format, but it was most common for 35mm.
I don't blame Christopher for the rush-hour job, especially the bizarre idea of buying up 10 years' worth of the stuff: IC materials are notoriously unstable long-term (assuming, by luck, the materials are not faulty to start with!) and I would bet they would not last 5-6 years even in cold storage before compromising changes take place. It's a risk he is obviously aware of.
Today the gold standard RA-4 print process is using FujiFlex CLAB Super Gloss -- virtually the same surface fragility and super high gloss finish that people have come to expect of Ilfochrome Classic. If I want to be reminded of the real deal, in storage exist 744 Ilfochrome Classic prints produced between 1990 and 2010.