I wasn't the one who noticed. I was in the car with a coworker playing a Metallica song. She went to music school and plays instruments, she asked why it sounded like the bass was trailing behind. I adjusted it, had her listen again and she said it sounded fine at that point. She doesn't know anything about car audio, TA, x-overs, etc.
Since you did point to science and because I am curious, what's our tolerance for delay in sub-frequencies before we notice it's behind and what's an average group delay in a ported enclosure?