The agreement is pretty vague on the subject but it seems that you can get permission to virtualise on non-Apple hardware. How one does this and if anyone ever has is another matter entirely.
Apple does it internally, since they can turn off the mechanisms that stop macOS from booting on non-Apple hardware (last I heard on HN, they ran it on HP workstations?). I'd imagine that if you got JAMF, Adobe, and Microsoft in a room one of them has the magic incantation as well, considering the amount of Mac code they put out.