He could take a bit of a gamble, do some Linux as a comparison and see if that draws viewers too, maybe some attention from those that are curious about Linux but not enough to actually delve into the topic themselves (or deterred by the reputation of Linux being complicated).

Choosing a suitable distribution might be a challenge, particularly because some distro elitists will inevitably come to dunk on his choice and he might not want the comment section to be clogged by distro wars (particularly if the majority of viewers, as you suggested, are Windows users and will find that off-putting).