Agreed, sort of. (I don't think Shardstone was suggesting making stuff up on the spot but rather working out the details in the background. I could be wrong.) Regardless, the Bastion and the associated rewards need to be tethered to the fiction for me to accept them, but I think the system can still be an abstraction of monetary transactions, political and social influence, connections, etc. I'd say for this to work at all for me and my table, it would have to be an abstraction, because, yes, I do logisitics for a living and I don't want to bring that level of detail into my game. (To be clear, I would expect my characters to engage with logisticis -- but I shun it as a player and DM).
If I spend Bastion Points to acquire a magic item, that item would not just pop into existence without explanation. Spending the points would represent the work -- tracking down the item, negotiating with the seller, hiring someone to steal it, or researching and implementing the methods to create it.