The WN flanges have their ratings reflect their working pressure in relation to temperature. The thickness of the weld neck of a flange or its schedule relatively corresponds to its rating. So the WN flanges are manufactured with their “standard” neck thicknesses already correspond to their ratings.

I always want to see the schedules of the flanges specified on isometric drawings and MTOs, do you think it’s over the top ?

Sometimes, we have the WN flanges to be welded to much thinner pipes. For example where we have spec break, would the suppliers bore the necks to match our requirements ?