What I haven’t seen mentioned in these discussions is where the mental association of “banned books” comes from.
In America, at least, the school curriculum spends a lot of time talking about dictators. It mentions, numerous times over many years of a child’s life, that something dictators often do is to ban books that could make people question them or that could make people support people the dictator doesn’t like, etc. In all such cases covered in the school curriculum, dictators’ “banned books” are not allowed to be sold in the country at all, and are often destroyed, sometimes even in mass burnings.
So, this is the psychological association people typically have with the phrase “banned books”.
The news articles over the past X years declaring something like “Government Y bans books!” seem to be leveraging this mental association to give people the emotional impression that Government Y is doing dictatorships things. I think this is why people get annoyed, since not allowing whatever books in the school library is not a dictator thing (okay dictators do it but it’s like drinking milk or being against animal cruelty, it’s not something that is primarily done by dictators).
So, when people say that not allowing a book in a school library is a type of ban, they are correct, but they ignore this association which most people have from school.