I'd argue: Yes, this is true. But you need at least on stable part in the toolchain for the kernel to get reliable results. You can't have your hammer transform to a screwdriver just because you swing it in the other direction. And if there is such a tool/case, you need to be absolutely sure how and when it behaves this way, on every possible platform.

This is not the case for evolving C++.

To me this situation is more more like having a screwdriver that can only be screwed with hammers from a particular manufacturer (Linux -> GCC), because that manufacturer is the only one that makes hammers with screw-driving tips that work with that particular screw head (non-portable macros for type-checking or whatever goes on there). You might as well just get a normal screwdriver (C++ compiler) and a normal screw (C++ program) like the rest of the world does -- and there's no implication that you have to keep changing screw tips (-std=c++??) every time Apple (standards committee) decides to come up with a new format (C++17).

If you are going to argue that, then you need to look again at the headlined item, where it was not the case that it behaved the same on every possible platform. It is a non-standard mechanism of one compiler, that was picked based upon a compromise decision about what versions even of that one compiler it would actually work with.