if the card has now been used for the first time
for TfL it can probably be used again in a shop without the first time PIN.

Except I've never been asked for that "first-time" PIN. Have you?

Nope. When I was in London last month I used my U.S. issued AmEx
card. Worked great. It has both a regular chip and a contactless
one, but AmEx is quite clear that there is no PIN.