I think that's just how it's displayed. Did you try registering your gift card, or just use the balance inquiry function?
Here's an example of the summary page of some registered cards:
Note that the balance listed here shows one card in USD and another one in CAD, so it does record the different currencies on the summary page.
Here's what I see when clicking to see the 'History' of the second card on the list.
Note that the balance shown on the transaction history screen flips over to the USD equivalent. However, the transaction history details are shown in CAD, which is the true value of this particular card. The values shown in the image were all CAD transactions, which also net out to the correct CAD balance shown on the earlier screen.
Therefore, I think it's just a glitch in their system, where it shows the balance on that particular screen in USD only. I think you'll be OK and that it is really all in CAD.
On a different but related topic...
I wonder if the implied exchange rate shown is an indication of the exchange rate that would be used if you used a CAD gift card at a US property? At the moment, it's 1.2531 based on the amounts displayed of USD$113.59 = CAD$142.34. The market spot rate right now is 1.2566. If so, that means that the Fairmont gift card system is only taking an F/X premium of 0.35% over the spot rate, which is a far better conversion than I'd ever get with any credit card when making a foreign currency purchase.
Perhaps I should always be paying for Fairmont hotels using gift cards denominated in my home currency?