Ignoring the results of feature checking when on a competitor's CPU is, though, and that's what they do.
Of course. This is obvious, if you had any idea about what you were talking about.
" I would only enable specific optimizations when I could guarantee the output would be optimal or a given model."
You can do that with compiler flags, ever heard of them?
If your CPU lies about its feature support, there are far, far, far bigger problems for the end user than whether a binary is optimal or not.
In this case, the optimal thing to do was not to use these instructions despite the processors claiming support.
They're already doing that by checking whether it says it's a genuine Intel. If you can't trust it when it says that it supports a feature, why trust it when it reports a manufacturer?