I have checked the Bad Boy and Base boyfriend routes, and they both have the adult CGs, but the flirt doesn't, ironically. I haven't played the Prince route on the computer I'm using, so I haven't checked those CGs, but I'm about to.
The Flirt's sex scene doesn't actually involve him getting naked on-screen, so there aren't any CG updates for that particular scene yet. We do have additional image variations for it, but the scene requires additions/rewrites before we can implement them. For further clarification, we have a separate update planned to add more choices to the sex scenes so that the player can choose to be dominant/submissive rather than having the scenes "on the rails," as per player requests.