Well they don't. The different models do indeed have differing tones, but for languages that are not english, available high quality data sources may be lacking diversity.
Also "slop" is so vague that anything can fit the term in ones subjective perception.
You hand out a token, often a json web token, to an authenticated user, which is then validated for each request. A token is basically a hall pass which is signed by your central authority. Depending on how "instant" removal of users needs to be, you sync with a central identity provider each time or you rely on short lived tokens.