Exchange rate for Wealthsimple Cash Card - No Fx transaction fee?

Hi everyone,

So I read a post here which mentioned that the wealthsimple Cash card (debit card ) doesn't have any foreign transaction fee similar to the newly launched visa credit card.

I'm visiting USA so I thought I could use wealthsimple cash card as I don't have a credit card with no foreign transaction fee. Yesterday I filled gas for 50USD and I see in my cash account I was charged 75CAD. That's exchange rate of 1USD = 1.5CAD. That's crazy. Even with a foreign transaction fee I would have got a better exchange rate on a credit card. Can someone tell me what's going on here ? Does wealthsimple have a fixed rate on wealthsimple cash card ?

Edit: The higher rate was only for the pre authorized amount.