Sorry to disappoint but this change did affect geocoding. It is a stellar example of something that might have looked like a bit of a simple cleanup but in reality was a structural change to the tagging that can suddenly pose quite a huge problem on the software side.
Here is the problem: we’ve had this double tagging of rivers with waterway=river/stream + waterway=riverbank. Often both were tagged with a name. This needs some deduplication for geocoding purposes. Nominatim did this by simply ignoring waterway=riverbank. After all, the river line is the more interesting result and ignoring a tag is easy enough. Then @ZeLonewolf came along and changed the tagging from a simple waterway=riverbank to natural=water+water=river. What was previously a primary feature now became an attribute to another tag. The way the tag processing works in Nominatim there is no way to filter by such an attribute, so deduplication of rivers has been broken since this particular mass edit because fixing it requires a change in the design of the software.
Please don’t discuss now the peculiars of how to implement secondary tag filtering. It’s not really the point. The point is that any changes to existing tagging may have an affect on data consumers that you don’t have foreseen. So if you want to have deprecation and ‘tagging cleanup’ in a major way, you have to devise a plan that gets feedback from data consumers already during the RFC phase. I consider any proposal doomed that cannot show that considerable thought has gone into the secondary effects that the change might have.