Some people think that publishing source code is first and foremost a way to get other people to collaborate on its development, not to ensure any particular rights or knowledge or safety for people who end up using the software. For example, you could imagine a consortium of people who each make a super-proprietary locked-down thing and they publish and collaborate on the code of some libraries that their respective locked-down things need. They actively do want other locked-down thing makers to comment on how to make the code better and contribute patches, but they actively don't want customers to use that knowledge to make the thing less locked-down (or to be able to verify what it does or doesn't do).

This is a situation that we often encounter in the real world, and in fact some of the locked-down thing makers are even surprised when people say the contrast in their behavior with respect to these audiences is strange or hypocritical, because they didn't know or didn't remember that other people think software freedom is partly or mainly meant to benefit users.