SIGMETs will be less accurate with boundaries, they have to be generous for safety’s sake. Whereas your link has much more defined boundaries for the various intensities.
The CAT map you’ve linked is exactly what we need! I hope they use that instead of the SIGMETs for CAT and implement full world coverage for all three intensities shown!
Edit: It’s even better than I thought! The CAT map is pressure altitude specific with 50mb increments! It would be amazing if they used that as their data source for clear air turbulence.