I'd guess that the CS rep was trying to expedite the removal of the fee rather than just letting nature take it's course, as it were. She may have thought she WAS explaining the authorization thing to you but for whatever reason, communication was just not happening.
As others have said, it's pretty standard, (she might have thought you knew that and were simply looking to have it removed quickly) but if it's the first time you've returned something, or happened to look at your CC statement at
just the right time, I can see why it was a concern!

Anyway, it's sorted.

Take a deep breath. . .it'll be fine.