Well, quite a few people think the tag system should be improved. Here it is additionally a scene that is (a) completely optional, and (b) does not involve the MC at all, which may make this even more confusing.
However, there is a good reason to include a tag after one scene, actually two.
One is the "butthurt" part above, phrased more neutrally "people want to avoid certain content". Tags are not only for finding content, but also for avoiding content. Just imagine a game where you frolic around, choose your main LI and then she suddenly jumps up in a train "everybody please fuck me" and everybody does. 600 renders and 43 animations. Only one scene of NTR - no need to mention it anywhere surely? People who do not like NTR will certainly be understanding, as they tend to be.
The other reason is that "a scene like this exists" is the only objective measure. If one scene isn't enough, how about two scenes? Three? Four? Where exactly is the line? How about a game which only has two very long scenes, one gay one straight. 50% of the game's lewd content is gay, yet no tag? If your answer is "it depends" you would be correct, but as soon as something "depends", people will have differing opinions. There can be no differing opinions on whether content exists in a game at all - so at least everybody can have the same understanding of the tags.
The problem of course is that this "understanding" is useless in many cases and can lead to false hope when seeing a tag and it is just this one scene. Which some players won't even see depending on their choices. There have been many ideas how to improve the tag system. Differentiate between "avoidable" and "forced". Differentiate between "theme of the game" and "occurs once or twice". Differentiate between "affects the MC" and "is happening in the background". Of course, all of this would make the tagging and filtering processes more complicated and convoluted, but somebody might find a solution.
More importantly though: There are many threads regarding this in the general area of this forum, different ideas. So far there has been no visible inclination by the powers that be to change anything. And as long as this doesn't happen, it doesn't really matter what you - or I - think about it.