Nah, it doesn’t just linearly double like that. If it takes 10 people to build, test, and support the launcher for Windows, it doesn’t take 20 people to support Linux, since most of it is going to be the same across platforms. A 1.8% increase in sales also isn’t the best prediction. On Steam, the vast majority of their players and revenue are accounted for by just a couple of the most popular games, and a lot of that is dictated by what games are allowed or successful in China. If your game isn’t selling in China, your addressable market is actually much closer to being 4.5% Linux. That’s not to pick on China, but China is a massive market on its own, and it’s the difference between the case where you’re selling microtransactions in Counter-Strike 2 or if you’re selling a metroidvania.
I think they’re called that because they postdate the “looter shooter” that combined Diablo-esque “action RPGs” with FPS games, like Borderlands and Destiny. “Looter” without the “shooter” is a much better name for Diablo’s genre anyway, since we have far too many RPGs that are also action games and have nothing in common with Diablo.
I’m still waiting for the resurgence of the style of shooter that came just after those that inspired this wave of boomer shooter; the likes of Half-Life, Halo, 007, TimeSplitters, and so on. I don’t know what subgenre will be assigned to those games when they start to come back around, but that style is also old at this point, so hopefully it doesn’t also get assigned the label of “boomer shooter”, because then it’ll be harder for both audiences to find what they’re looking for.