The CAT certification is by the aircraft manufacturer.
The 8168 final approach CAT is based on the speed of the SEGMENT, FAF to threshold, not crossing the threshold. There are other segment and holding speeds per the CAT.
You can go up a CAT by going faster, if conditions warrant and the regulator allows. Many CAT C aircraft, esp 737 variants, use a CAT D approach speed and minima, IF they are authorized...