mongirlfan said:
Because it's... weird? Should we treat Astolfo at all times as a female except when his dick is out?
It's not just weird, it's a horrible idea. Some might say people doing girl focused searches would want things like this included, and I wouldn't say you're wrong, but how many posts do you actually think that's going to add to a search? Posts where Astolfo's gender is truly ambiguous are actually pretty hard to come by, and he only has around 5k posts. 1girl has almost 4 million. 1boy is only 800k, and otoko no ko only 36k. You're not gaining much by deciding that all feminine boys be tagged as girls.
Not to mention, that way of tagging would completely ruin otoko no ko and crossdressing. We know this character is a boy, because there's information available somewhere that says so, but we're tagging him 1girl cause he's dressed very convincingly as a girl, but then it doesn't make any sense for us to tag it with either of those tags, because 1girl wearing a dress isn't crossdressing nor an otoko no ko.
That's not even the worst consequence. TWYS has never been an ironclad rule, some things just need to be tagged using outside information. If we decided that the gender tags should also ignore canon information and adhere strictly to TWYS, then all consistency and reliability goes out the window. Even if it was limited to certain characters, like Bridget or Astolfo, it would still be an utter disaster. It would turn the gender counts into subjective messes, where anyone would be justified coming along and saying, "this character is tagged 1girl but I think they look like a boy, so I'm going to change it to 1boy instead." and now we have people arguing constantly over whether or not this or that character is more feminine or masculine in this or that post.
Sure, something like e621's "male (lore)" tags might get around some of these problems, but on top of just being ridiculous to make however many stupid looking (lore) tags would be needed, it's just a pointless circle. "Male (lore)" is literally just our 1boy, all we'd have done is flip our gender tags upside down just to remake them under a different name to fix a problem we made for no reason.