That is not the logic in SAP, it is always the shipping plant which passes its commodity code.
Just imagine I am a vendor to your Canadian plant and I sell you some materials here from Germany. I do not at all know what HTS code you have in your material master in Canada.
Nevertheless I am able to sell goods to Canada, and I am sure you get it cleared at customs.
the first 6 digits of the code are harmonized globally.
If you have a total different code in Canada than in the US then there is certainly something wrong classified.