I mean if they were? Yes.
It seems like you have a liking for defining things according to what more than 50% of people do.
I'd like to emphasize the "you can't" in the hypothetical statement. There are issues in this mode of thinking:
1. The people who emits that statement impose themselves as authority who defines definition and concept. But definitions and concepts are subjective/personal tools to navigate the world first, and tools of communication second. Hence, words often appear in the culture first, and are recorded into dictionary later.
2. The hypothetical site can be considered both as hentai site and not. Real objects are often complex enough that they cannot be categorized with a single sortal criterion
Your statement:
Bad methodology. Just because there’s more non-smut novels, doesn’t mean people are reading them.
implies that you think your implicit definition of smuthub is better and more objective than the other party, and impose it as hard fact without attempt to establish a consensus on the terms of communication.
I'd like to point out that defining smuthub based on 50% reader activity is as subjective as 80% 20% cut off. Even the consideration of the userbase itself is subjective. I find it strange that you can't conceptualize an object in itself without having to consider its environmental context. I feel like there are some serious dependency issues on how you model the world.
In addition, you disallow yourself from conceptualizing things until you have collected enough data from users. For instance, if you haven't checked that more than 50% use their phone as a tool of voice call rather than a entertainment device, you can't categorize as neither without making a baseless claim. And then after categorizing (let's say phones are entertainment device), you somehow reject the other definition (phones as communication tools)?
On the other hand, OP used the simplest and loosest concept of smuthub based on the personal experience of how many type of content is thrown at the reader. This is the smallest scope possible and I find nothing wrong with using that approach.
Regardless of intended function whatever the userbase determines a site/program is used for is how itll be known. Theres probably other examples of this with other apps or sites but I dont have the brain power to look them up right now.
It's because the unintended functions are good, not because the userbase collectively decided to agree on a way to conceptualize the thing. No one sat on a round table to hold a council, "yeah let's spread the glorious scribblehub as smuthub" and yet we all marvel at the abundant harvest of spicy stories. I would be cautious on the order of cause and effect of your hypothesis. In addition, if everyone used the site/program as intended initially, doesn't that forbid the first user to distort the image of the site/program from its origin? For instance, the first one to realize and say tumblr is a nest of horny degenerate is wrong.
In conclusion, it's perfectly valid to criticize the small scope of OP's evaluation. It's also appropriate to suggest to widen the scope to userbase to fuel a more exhaustive judgement. However, disregarding this aspect is not a mistake even if it doesn't satisfy your standards.
bro why do I yap so much just to say that I don't give a shit about other users when I judge stuff?