If it runs your container just as well, well, it's "Linux" as far as your app is concerned.
Case in point: 1% of Google Cloud Run could just as well run on Fuchsia today and you just wouldn't know. All you see is the inside of the gVisor sandbox -- yet at the same time it'll run pretty much any http-serving docker image.
(Of course, in the real world Linux rules because of its huge collection of drivers, filesystems, etc.)