When did "PC" and "Microsoft Windows" become synonymous?

JrbuPTur writes: There seems to be a common theme emerging in game descriptions lately; they market themselves towards "PC and Mac". Naturally I'd assume that it would run on Linux — but that's not what they mean. So far I've backed 7 games on Kickstarter, and ALL of them do this. If you search the Kickstarter project descriptions for "Mac" or "Linux", you'll see it: Nekro, Leisure Suit Larry, Starlight Inception, The Banner Saga, Shadowrun Returns, Wasteland 2, and Double Fine Adventure. Many of the people who created these projects are programmers who made software for IBM compatible PCs back in the day. I refuse to believe they are unable to make this distinction, so are they just catering to the masses? As a side note, all 7 projects have actually pledged to create a Linux version of their game.