You’re a customer of that bank and they almost kicked you out because you wanted to discuss THEIR restriction on how you can spend YOUR money? Time to get another bank… 
I don’t doubt that there may be a bit of “maybe they’ll forget to cancel” in their decision-making, but if you read the blue post, it clearly said after “a review … in all currencies.” I mean you can ignore what they tell you is the reason and make up your own, but if it’s a currency thing then the cost to Blizzard for converting lots of $15 USD equivalent transactions into USD is clearly large enough compared to the cost of half as many $30 USD equivalent transactions that they decided to make this change.
PayPal skims money off the exchange rate at a percentage on top of a flat-fee when I send USD to my kids in Canada, and it’s similar for any business offering currency exchange. Blizzard needs to convert Canadian/Australian/New Zealand Dollars, Brazilian Real, Mexican/Argentine Pesos, etc. into USD on a monthly or quarterly basis and there’s a cost for doing that.
What the blue post did not explicitly say is that they don’t want to give players that pay for game-time with gold discounts anymore, yet that is obvious from the removal of any discount options for game-time (while subscriptions for real currency rather than gold still offer discounts for large blocks of time). After all, why should they give a discount to a transaction that they make $5 USD net revenue ($20 token - $15 game-time) rather than force people to pay $13 USD in real currency for a discount?
So…
- Reduce the cost of lots of tiny foreign currency conversions into USD (stated objective)
- Eliminate discounts for “free-to-play” players that pay with gold
Sucks for F2P players or those like @Clunk that have a valid reason to pay for game-time as a gift rather than just get a sub, but not unexpected from a for-profit company that is pretty sure they will still reduce costs more than any lost revenue from quitters–net result increased profits.