Does treble response beyond my hearing matter?

On the grand scale of things, no.

Fin,

If the specs look good up to the limit of your hearing, you are probably in pretty good shape, no matter what might be measured beyond.

When I was young, I could hear test tones up to 20khz. Now, at 54, only up to about 12-14 or so. That's typical of how our ears age.

It can be a good thing though. By design, not much music occurs in the upper ranges of human hearing, but a lot of noise and distortions can. So not being able to hear up there can be a blessing. I find most music a lot less fatiguing these days than I did in my youth.