Hello,
This looks like a mechanical edit, and if so, should have followed https://wiki.openstreetmap.org/wiki/Automated_Edits_code_of_conduct .  I don't remember seeing any discussion that said that you were going to do this.  This is relevant because there are data consumers of this tag https://taginfo.openstreetmap.org/tags/waterway=spillway#projects - each of those projects has a contact mechanism (in many cases you can just raise a github issue to say what you are planning).
Best Regards,
Andy