I love reading the comments on Mac Rumour articles when it's negative news for Apple's platforms or services. To paraphrase: "Vulcan bad!" "Lazy Devs!" "But they support Linux?" and "What a dumb business decision!"
Yes, Apple zealots, Valve is absolutely going to support your vendor-specific graphics API on a platform that they aren't making much money from, and will continue to support and test that platform for years, operating as a charity because they love Apple so much π