It has 8 GB of RAM. Mike Rivers does his research and rarely gets a spec wrong, so he may have been given an incorrect spec...or someone confused the 3 GB cache spec or something. Or it could have been a typo, given that it says "4 GM."
FWIW the NUC is not an off-the-shelf computer, it's quite customized. Actually that's the whole point of the NUC...it can be customized for particular tasks. That's why Intel makes so many variations on the concept available, and then companies like PC Audio Labs can take that even further. As far as the black-and-white insert in the video goes...humor doesn't always translate, which is why it's always safest to avoid humor. At least on the net we have smilies to indicate "humor alert."