I understand your position.
Yes, it is a strange story.

By one hand, if we try to change something, we haven’t a validated ASME approach and we would only guess something congruent with.
By the other hand, maintaining "as is" this ASME design mathematical model for the flange checking purpose, we have strange results, which is evident when the pressure loads are substantially less than the rating pressure.
Including the external loads is possible only via "PEQ" methods just because some PEQ formulas are included in ASME Codes or worldwide accepted. But the truth is there isn’t a PEQ formula able to make a true equivalence, because the flange stress under a bending moment isn’t axial- symmetric. One formula is able to count an equivalent stress on gasket, but the flange stress is not proved as being equivalent. And so on…

Best regards,