to add to this: apparently there’s more evidence from TianYanCha (gov platform with data on Chinese companies' intellectual property holdings) suggesting that tracing is chronologically impossible:
hoyo’s last 2023 copyright registration for lightcone art was on 8.4.23, the disputed fanart was published later, on 8.19.23. legally, there’s no ground for the artist to sue as the final victor was probably among those lc finalized & submitted for intellectual property protection before the fanart was published