Apple has implemented per OS security. Meaning that you could have complete chain-of-trust with one OS and have an untrusted second install of another OS. No PC has that, and it’s the core idea that allows Linux to be ported. I don’t see how such a useful technology for testing insecure versions of macOS would be removed. Apple backs few technologies, but they don’t often change their mind when they do. The fact of the matter is that Apple benefits from the access it gives Linux. It won’t remove it thoughtlessly.

Ultimately it leads to a discussion about the competition. When you buy an ARM based Surface, can you put Linux on it? Is Microsoft clear you can? Are they providing drivers?