I think you keep forgetting that people have to apply for the card. Approval can be instant, or it could take 7-10 business days, like every other credit card. In addition it then takes a week to receive the physical card. So transactions will be down until people actually get the card, because ApplePay is still not accepted everywhere.
The number Apple is more likely to show off is how many people applied for the card.
I found the exact quote from the Jennifer Bailey during the Keynote-
“You don’t have to wait days to get your card. Just sign up on your iPhone, and in just minutes you get your Apple Card and you can start using it right away”.
I already address this in my first post. If they don't accept ApplePay, the Apple Card will not work without a physical card. That has nothing to do with instant approval.