A copyright assignment doesn't need to be public. An employer might not own anything we create in our free time, or there might not be an employer at all. And

A copyright assignment doesn't need to be public. An employer might not own anything we create in our free time, or there might not be an employer at all. And if I put that I worked on a project under a pen name on a resume then I would include the name I worked under, accepting that it is probably not that anonymous anymore.