I know my opinion doesn't mean much but for digital codes, I've never seen a major trading site allowing someone to trade for items the seller doesn't have on hand unless the seller is buying immediately on demand and the trade commences almost immediately. It offers zero benefits to the buyer and puts all the risk on the buyer. If the seller can't acquire the game, then the buyer is screwed, even if they get a refund. Ultimately, their time was wasted and they still didn't get what they were seeking in the first place. This is all assuming there is no malicious intent, of course, since allowing that much of a time delay in sending the digital key increases the likelihood of multiple people being scammed before the ruse is discovered.
BernardOne seems like a reputable seller with no ill intentions. That being said, policy shouldn't give exceptions to one individual, it should be implemented without bias and think of the larger community in general.
At the bare minimum, I think disclosure should be required. Items that aren't immediately on hand should be noted as such and the buyer should be made aware that delays are possible, assuming they are able to get stock. If the buyer is comfortable with those terms and the potential for not receiving the key at all (and thus being refunded later), then that's their prerogative.
