It's strange to me when someone says they only know backend or frontend. Does that mean they literally never worked on the other side, like not even knowing Ja

It's strange to me when someone says they only know backend or frontend. Does that mean they literally never worked on the other side, like not even knowing Javascript or other language? I've never worked as a developer and learned how to make apps for my side projects, so from the start I had to learn a bit of both. Obviously not as deep as someone who calls themselves exclusively a front or back end developer. Does just knowing one side signal that you only do development for a job?