The changes to CvCity.cpp make it clear that the patch note correctly describes the intended change (which does not match the actual change).
So I assume in the unofficial patch for 3.19, the game is going to be fixed to be more like the UP for 3.17, where overflow gold was still allowed but not put through multipliers, and that based on what the intended change was from reading the patch notes, very few players will object to this change.
I'm still surprised this was stuffed up. It's a pretty damn easy thing to test in 30 seconds.