No, I'm saying that there could be anything from a one word change to the standard that doesn't affect compilers at all to safety by default with a clang tidy performance warning.

Clang tidy and the core guidelines have already broken the textbook Hello, World! with performance-avoid-endl warning, so I don't see why the common textbook way to write things should be our guiding principle here. Of course, the common textbook way to write things would continue working regardless, it'd just have a negligible performance cost.