You're looking at this from the perspective of someone who is actually using this specific library. The issue is that it's cheating on a benchmark.
The large majority of the code people actually run isn't written by Intel or AMD. We use benchmarks for comparison because it gives people an idea of the relative performance of the hardware. Reviewers are not going to test the hardware against every individual piece of line-of-business software or in-house custom code that people will run on the hardware in real life, so instead you get a sample of some common categories of computer code.
Optimizing the benchmark for one architecture and not the other is cheating because it makes it no longer a representative sample. Real third party code is generally not going to enable instructions only for Intel and not AMD when they exist (and improve performance) on both, it will either use them on both or not at all.
The large majority of the code people actually run isn't written by Intel or AMD. We use benchmarks for comparison because it gives people an idea of the relative performance of the hardware. Reviewers are not going to test the hardware against every individual piece of line-of-business software or in-house custom code that people will run on the hardware in real life, so instead you get a sample of some common categories of computer code.
Optimizing the benchmark for one architecture and not the other is cheating because it makes it no longer a representative sample. Real third party code is generally not going to enable instructions only for Intel and not AMD when they exist (and improve performance) on both, it will either use them on both or not at all.