Notice how the payment transaction actually happens in Apple Pay. So that means that you need FaceID to complete it. Impossible to do if the phone is in your pocket!
I believe the route to the accidental purchase the twitter thread refers to is through the "Pay with credit card" button though, which for some reason isn't present in your configuration.
Making a conscious purchase and then regretting it (after getting yelled at by your wife) does not equal to a "fat finger incident".