Who’s saying that everyone should get the same stuff? Or hear the same details? People should use what meets their needs.
As to tonal quality, I have a theory, nothing more...it’s based on the idea that lots of little things add up.
It’s generally conceded that 30s and 40s Martins have a special sound. A lot of that - most of it, probably - has to do with the bracing and other construction details. But it’s also interesting that Martin started the 30s with ebony truss rods, then moved to a T-bar non-adjustable metal rod that they used until the 80s. So, Classic Martins have different truss rods than modern Martins. They’re also regarded more highly. Why?
Here’s an article showing the rods in cross-section:
https://hazeguitars.com/blog/martin-guitar-non-adjustable-truss-rods
So here’s my theory:
Everything in the neck of a guitar vibrates, and therefore has a resonant frequency. Vibrating stuff makes sound. Tap on a piece of metal, it rings.
An adjustable rod uses a hollow tube with a metal part inside to tighten and loosen. It’s different than a T-bar in shape and mass. It will resonate a certain way. A solid metal rod also resonates a certain way. I’d imagine carbon fiber has its own resonant properties, but they’d be different from metal.
As we know from experience, a maple neck has a slightly different sound than a mahogany neck. We also know that the neck is an important part of the tone-generating on a guitar, since it touches the strings, and since it vibrates even more noticeably than the body when a note is plucked. So we know that what the neck is made from matters. The fretboard matters. Hell, what the nut is made from matters - most folks can hear the difference between a bone nut and a plastic one. Put a microscopic coating on a string, it’ll sound different because the coating affects how the string vibrates.
That being the case, why shouldn’t the truss rod materials matter? They kind of have to.
The two PRS acoustics I’ve had with the carbon fiber rods have had an unusually sweet and woody tone - for whatever reasons. I can only guess! Perhaps one of many reasons has something to do with not having a hunk o’ metal in the neck?
As I said, it’s just a theory. I have no way of proving it. But I like what I’m getting with the carbon fiber rods. It ain’t broke, so I ain’t fixin’ it.