-But there is yaoi in this. Tag should be removed.
Well THAT'S. THE. POİNT.
No, the point is that some people can (be triggered/have their moods ruined) by a varying array of circumstances, and these people need to be able to rely on and trust the tagging system to get the best usage our of this site.
Even if the tag is technically accurate (and that's debatable) it is still used in a deceptive manner to spring a nasty surprise on the people who are trying to avoid the very thing they have been tricked into seeing.
A more useful and considerate tag would be something like yaoi on pages 19-22, or for those of you who might want to argue the technicalities implied yaoi on pages 19-22. That way the people who are here for yuri and nothing but the yuri can stop at page 18 without being lulled into a false sense of security.
It's just basic etiquette.