Actually this worked for me on 1st gen Apple Watch (iOS 12.4 I guess). But then I unpaired that watch and paired it with the new iPhone 11 Pro. Now it doesn’t work :P
I have several transactions with Apple Card already over the course of the past couple weeks and never used Apple Pay with my phone before (always with the watch) until yesterday when I was in a drive through line and realized Apple Card was (strangely) missing from my watch.
Based on what I’ve seen, the only reason for preventing Apple Card on the original watch is to encourage everyone to buy a new watch, which I’m sure I don’t want to do right now. Even though the new ones have an always-on display (cool!) they’re too expensive.
That said, my ability to use Apple Card was likely a “mistake” that they are “correcting”, which is pretty depressing.
Anyhow, my solution was to sign up for a new card to replace Apple Card... one that earns 2% back for all purchases regardless of whether you’re using Apple Pay (won’t put it here, just Google it if interested).
Apple Card is great for purchases with Apple (services, hardware, app purchases), but I don’t think these restrictions on Apple Watch Gen 1 can be justified in any way when there are other cards that earn more cash back and also don’t have any annual fees. It’s a shame, I would’ve loved to use Apple Card everywhere.