It's just like that in asian societies man.
Just turn Yeomin's gender from male to female and you'll hear a lot of dumb rumors like that all around you.
For example, there was a rumor going around in my college that my friend was working as an escort because she "wasn't that pretty" (still so flabbergasted that they used this reason btw), by my country's standards of beauty, just because she used different branded bags everyday, she's not, she just comes from a very very rich family.
Another example, I had a rumor going around that I had a secret OF just to pay for college when I didn't, I just liked posting my gym photos on my insta and am still in debt from college lmao. Also if I did have an OF why would I even keep it a secret?
All because asian society still runs on conservative biases, jealousy, and misogyny. Because if girl has nicer than nice things? Sex work. If girl likes posting photos of herself? Sex work.
Now imagine all that, but multiply it by 10x when you go to Korea for work and start living there. It's depressing but that's just life.
╮( ̄▽ ̄)╭

Those are some shitty people in his college, I'm not even gonna lie. Who the fuck cares? You do what you gotta do to survive. As if they never saw him juggling part-time jobs before he met the ML. Suddenly he's a bad person for accepting help from a sponsor? Gtfo