That's not the point though.
As I said before, pixiv/seiga tagging is pretty awful because artists and users aren't encouraged to keep it standard -- it is nonstandard by nature. If you want to find posts from them quickly, you use this as an auxiliary search to get to the posts you want to find, even if you can't see the posts. For one thing, pixiv intentionally has everyone wait however long before adding or removing tags (can be anywhere from 10 minutes to a half hour or longer), and they always alert the artist of any changes (and more specifically by default, tag removals). This has gotten me blocked by an artist once, which is why I'm keen on not tagging so aggressively on pixiv anymore unless I like a post a lot.