Sadly they didn't test older mechanical keyboards like the vintage IBM ones. They always felt insanely quick to me.
They have tested IBM Model M and as it turned out wired latency for that keyboard is only 18.6 ms. So not fast compared to others, but they have a unit from 1993 and around that time IBM reduced manufacturing costs so it's possible that earlier versions were better in that respect. Also, I wish they reviewed modern Model M by Unicomp, because it's still produced and is relatively affordable.
https://www.rtings.com/keyboard/reviews/ibm/model-m
Oh nice, didn't see it in the List you posted! 18ms is pretty hefty you are right. I played with a Model M from 1990 and I had a Model M2 which was from 1995 or something. I liked the 1990 more but the M2 was good too, better than most trashy rubber-domes I had at the time.