Stiffener Design as per AISC vs CSA

[EngDM]

Here is my situation. I am designing stiffener plates for a column bearing on a beam. CSA gives one equation, and AISC gives another. They take different approaches for determining what the bearing length N (lb in AISC) is for web crippling calculations. CSA takes presumably takes N as much larger (they only provide one example using this equation, and it is connecting to concrete), allowing you to use the entire bearing width of either the cap plate or the concrete wall you are bearing on (or use the baseplate from the column if you are loading from above). AISC takes N as t+5*tp in accordance with DG-24.

For many calcualtions where CSA does not strictly have instructions, they themselves defer to AISC 360.

My question, if you could call it that, is if CSA typically defers to AISC, why do these equations/approaches not follow suit? The CSA value for web crippling seems MUCH more unconservative in comparison to AISC. Without the forethought to consult AISC, a designer trying to comply with CSA might not think twice on this calculation.

I'm curious what the other Canadians on here do in cases like these. A lot of the times, if calculations are provided in AISC, the CSA version is quite close (for example welds, we have different phi factors but it works out to the roughly same once you actually perform the calculation). Do you use the more conservative method, justified by the use of alternate codes sentences in the NBCC?