defacto, Bloggs,
The aircraft CAT is set by the manufacturer, and that is worldwide, note the table Boeing table from the previous post....
The CAT is NOT based on MLW, nor max flaps, for that ac. The ref CAT also does not include any winds. The manufacturers certainly play with the numbers a bit, but that is their call.
For your edification, I looked it up on the 737-800 QRH.
The Boeing cert table shows the 737-800 approach speed at 142kts....(MLW is 73T)
from the QRH, that is 60T flaps 30.