Bingo! You referring to the particulars of the contract ("purchase agreement"), and not of the transaction (Point of Sale, translating to Place of Purchase in Citi's lingo).
There you go again -- "(legal) place of purchase" appears to refer to the place of contract formation, as opposed to the POS.
Why would Citi contemplate something in their cardholder's agreement, which they have no possibility of determining (e.g. the place, where the contract was formed), as opposed to the Point of Sale?
I think we need to agree to disagree.
As a purchaser I only have the knowledge of the legal place of purchase and no knowledge of "point of sale" or any of the back-office operations.
To answer your question, I can only speculate that Citi introduced the change in their nuisance fee to scam more people and didn't think about the fact that they would be entering the unfair practices territory by using a back-office indicator hidden and unknown to the purchaser ("point of sale") as a proxy for the criteria stated in the terms and conditions, which is
known to both parties, the (legal) place of purchase.