That is not at all how I've seen it used. That may be where the original historical medical usage in Japan usage of Futanari came from but futa and shemale are both used for pre-op MtF transgender,people who present with significant breasts and obvious male genetila and related groups (although generally not consider an appropriate term for either).
I don't think these should be synonyms except [masochism - masosub]. Enjoying pain is very different from sadism, and dom/sub dynamics don't necessarily include either.
So, 'girl cock' does sometimes have a different meaning from futa, and has more trans vibes. Will keep the dickgirl/girl cock tags separate from futa.
Fair. Will separate the sadism/masochism tags from the dom/sub tags.
Rather, I made them Synonyms of 'SFW', rather than merging into 'SFW' (as it was) or Synonyms of 'possible smut' (as you suggested), but I did move 'most SFW' and 'mostly SFW' into the Synonyms of 'possible smut'.
No one claimed they are. They are however what english speakers (and AFAIK most of the western world) means when they talk about "Futa" and more relevantly to this thread - how the tags relating too "futa" are used.
'slash' seems to just mean 'gay', so adding to the gay Synonyms.
There are atleast two reasons to tag your thread. One reason, as you've pointed out, is to help people search for your story.
Another demonstration (like Futa) of how the people use a word can change from the meaning when it was coined...
Fun history behind how slash came to mean gay. It came from old fanfic descriptions where they included pairings like: Spock/Kirk, and since when you say that outloud, you say 'Spock slash Kirk', well, that came to be the pairing, and since so much of that was gay pairings, 'slash' came to mean 'gay' in time.
Noting for the record that it's currently 24,468 tags, so we'll see how much that gets reduced by after I do all these merges. That won't capture all the Synonymising, which links the remaining tags, but it'll be a partial indicator of progress.