If this had happened in any kind of regular manner in the past 10+ years, there would have been several threads and folks would be chiming in. While it is very hard to prove a negative, it is very unlikely it ever happened.
If you never actually incurred the 10% charge and were just scared off by someone mentioning that you were simply misled by whoever told you that. Again, there's no charge for getting your OBC back on your card.