There is a gulf and many shades between "this code should never be on an internet-connected device" and "it doesn't matter if this code is copied everywhere by absolutely anyone".

To me "highly confidential" would mean "isolated from the internet" or else it isn't going to be "highly confidential" for very long.

Have you seen a lot of code from Klarna, Storytel, Spotify (companies I've worked at)?

None of these companies are isolated from the internet.

I bet their devs are.