Your conclusion is correct, but the reason I take issue is that that’s not the thesis of OP. OP’s original subject/headline suggests that, or questions why, Rust is generally slow vs PHP, and uses a regex example as the “proof”. A person who didn’t read the Reddit comments, or who is less versed in critical thinking, may accept the example as a valid proof of the thesis, instead of simply noting the fact that Rust may not be as good at regex as it is at other things. If the Reddit subject was “Rust is worse than PHP at regex”, nobody would bat an eyelid and the resulting conversational threads would have a different tenor (and your conclusion would and should be the same).