Yep. I didnt know about that so I tried manually and it was largely impossible without luck. I saw the button change once but by the time I got into the link and clicked add to cart it was already gone. I think it keeps the stock for you if you manage to add.You need to use an API to get stock drop alerts. If you are relying on manual refreshing you are unlikely to succeed.
I ordered almost an hour after launch via an API and got an FE. I was hoping to get an AIB then 45 minutes later saw that there was 0 stock of AIB cards so casually tried for an FE. I didn't even rush through the checkout. I only made sure that all my address, card details etc were available in Firefox autofill and my bank transaction 2FA was to hand to use ASAP.
Another reason why this is such a mess though really. Shouldn't have to be in the know to get one. It should be accessible to people going to the website normally...