As someone who worked in the main game retailer in the UK, I understand stock shortages - but as you point out, these are keys. Publishers on Steam can click a button as many times as they like for no cost and generate keys, I can't imagine it'd be different for Origin (especially as this is EA themselves, not a third party).
They must also know what damage this may and can cause their brand, so a decent store would honour the release pre-orders - especially as you're made to pay upfront, unlike retail where it's either free or a £5 deposit. Therefore I imagine, if they had the choice, they'd eat the loss and bump up launch day prices.
Granted, all the above is speculation, but there's a high chance this points to getting the keys from someone who isn't EA, meaning they are no different to CDKeys, G2A, Kinguin in this case (whether that's a bad thing or not is a different discussion).