This is how it works, basically, except 1) you're not allowed to contact users about tags, even in cases of clear-cut tagging mistakes (like mispelling a character's name), and 2) there is a LOT of resistance to actually informing users how tagging works, what it's for, and laying down some basic guidelines for how to effectively tag your fic, apparently in the name of not stifling diversity or something. This leads to a lot of unnecessary work for tag-wranglers, who have to go through and make every random misspelling and slight variation into synonyms (which can get REALLY complicated when you move into tags like genres and tropes), and their workload also gets much larger the more works are coming in. Autocomplete has helped a bit, but it's not enough.

Basically, whoever came up with the way tagging works on AO3 can't decide if they want to be a useful searching tool for readers or an additional way for writers to freely describe their content, and it ends up being sort of neither.

/another former tag wrangler. I didn't last long, even though I love tagging.