R.e. your second statement, I can only presume that you're right, but I'm confused about how this works with copyright license agreements, or the cases where projects have had to go and get copyright releases from authors of individual lines of code to make a license change. If the copyright is on the entire work, how can a contributor of just one line of code own the copyright? Anyway. You seem more versed in this than I am, so I bow to your expertise.
In that case, there would be multiple authors of a single copyrighted work. I'm only familiar/knowledgeable with GNU copyright assignment, however, not copyrights in general. https://www.gnu.org/licenses/why-assign.en.html
