Yeah, I do this for plex as well, and stash. I think if the file already exists in the directory vlc should use it. It’s up to you to generate them. That is exactly how cover art for albums on songs worked in VLC for a decade before they added the feature to pull cover art on the fly.
We are well beyond that with these platforms now. They will identify your location and only abide by those laws based on where you are. This is how many many many subscription sites enforced California unsubscribe laws for years already