The whole profile is considerably sketchy. It plops what looks pretty close to official art between a bunch of Koikatsu and AI slop albums. I'd take significantly more issue finding a "gem" in a profile that's just full of crap like this since it can't be trusted to be from the account themselves (as in, it could be a reupload or edited image). That's probably way more of a red flag to not upload anything from them.
That being said; guidelines for paid rewards are in their wiki. One-time payments are not as long as the payment is not for a current or past reward. In this case, if I understand right, they're saying you can get proper art for 6 RMB - so no, it wouldn't be a paid reward because you don't need to subscribe to anything.
