Cool, that option is exactly what I needed and it now works as I would expect on a clean Kodi install.
I would really ask for that to be option to be enabled by default so others don't end up wiping their whole TADB rating history accidentally. It also probably needs a fat warning string saying this can remove ratings from theaudiodb.com. I'm still struggling to think of a scenario where it is useful to delete ratings from the "cloud" even though logically it is correct.
I think we are there now, thanks for the help