Gnadenberg I don't understand your confusion...transport category is transport category. It matters not whether the label on the control column says Boeing or Airbus.
The A340 at Toronto was perfectly serviceable...up until it speared off the runway end and burst into flames.
This stuff is not Monday morning quarterbacking...it is airline pilot 101. How can I land on a runway in the conditions that exist at the time (who cares what the conditions were 10 hrs earlier) if I am unsure of the LDR + regulatory factors.
Whether you apply straight 1.67 to good, medium or poor braking distances or divide by .6 and multiply by 1.15 the answers won't be too far adrift from each other. In fact the Airbus method will be a little more restrictive.