Doesn't matter since he say "we want it for free" which clearly we don't require. At least not in the case of HB.
However one could argue HB is close to free and maybe more Windows users buy their games over on say Steam sales or such whereas more Linux users watch HB because they wanted Linux games.
Then again it's "beat the average" for the extra games and there's no reason to over-do it unless you want too.
And Linux users may do it more.
However HB also used to have two tiers and now often have three and the lower level was even PWYW including $0.01 (still is but with no Steam keys) and since in reality it could be the case the upper tier games wasn't for Linux (or the other way around) that could affect things, or how much the individuals wanted each tier, or in the case there was bots / greedy people who just bought a bunch really cheap and those just happened to run Windows.
Whatever.
I'd say things are more pricey and people seem more willing to pay on the Apple platforms.
Whatever actual price is all that important for Linux users I don't know. Windows is used by a lot and lots of kids who may pirate more whereas Linux may draw a little more mature crowd who can also more easily afford paying (same as with users of Apple products.)