@Kyr0e but random door knockers is not what this situation is - it's a particular fame event you get after reaching a certain level of fame, a person you know will drop by to catch up (whether it's for a genuine friend moment or someone capitalising on your new fame). It's someone you already know and not a stranger in this case.
They just happen to spawn in with already greeted status, meaning they don't need to knock on the door. I think that has to be intentional, because the default state for visitors isn't for that to happen. So they must have made it that way.
There are other incidences where the game takes away your choice for whether sims can invite themselves in - vampire attacks, goofball/erratic neighbours in apartments, keyholders dropping by for unexpected visits.
So that's why I don't think it's a bug. But I definitely understand the feedback – some people just don't like not having control over visitors and want to reject all callers. I wouldn't be opposed to them changing it so that the person arriving has to knock first, but I'm just giving my assessment that they probably would put this to the bottom of their fix waiting list if it's something they created that way from the start vs something that changed and broke after a patch.
I have a bug I reported with DJ custom mixes I posted in 2017 or 18 and it still isn't fixed because the game shipped that way, so whoever they get to test it probably looks at the launch version and says nothing changed, so they never fix it.
