I would be thrilled to learn that Apple plans to prevent anyone from running non-Apple-signed code on the Mac, because it would likely lead to better tools for writing iDevice-targetted software on non-Mac platforms (either officially supported, or jury-rigged by third parties out of necessity). As a Linux desktop user with an iPhone, this would inevitably benefit me (I don't write iPhone software right now, but if there was an iPhone compiler for Linux, I might start).

Why do you think Microsoft bothered with WSL? We know that most Windows users won't do it. It was a developer-attracting move, meant to make it easier to build Windows client applications with Linux server components. Apple benefits from the same thing being offered natively. I can't see them abandoning it, even though it does create a tension between the Mac as a consumer product and the Mac as a developer's tool for iOS.