NPC celebrities in game do have the visual effects of being a celebrity (the stars), however they are not otherwise recognised as celebrities. Other sims don't react to them, I can introduce myself to them as if they were not famous, and there are no options to ask for autograph, photo or the other celebrity interactions.
I have the pack setting "Sims begin opted out of fame" enabled, and I think that could be related to this bug as a while ago there was a related bug with played sims gaining fame when they weren't supposed to.
I have the above setting enabled, and the pack settings carry across saves. So I think the above setting is somehow applying to NPC celebrities at the start of a fresh save. I tested by playing as Judith Ward in a fresh save with the setting enabled as default, and her fame info in the ui said "Staying out of the spotlight", despite her having celebrity fame point traits and visual effects.
