Thanks for these very interesting thoughts. I think that you are probably right about the 1st print. I am less certain about a separate print 2 & 3 based on size alone. Back in the very early days of the hobby the print runs were done on small presses with less strict quality control than later (and often larger) print runs. As a comparison, I have a few 1st prints of Runequest (here there is, as far as I am aware, only one 1st edition and printing) and they all vary a little bit in height. The booklets in early D&D sets vary a bit too.
In the bookselling world, variations within printings are dealt with by using terms like states and issues (e.g. if a printer notices a typo or poor layout while doing a print run (or, I guess, changes paper stock slightly) and makes a correction, then that is referred to as a different state within the 1st print. The important point is that it makes no difference to the date of the printing. In many cases, two different states will be bundled together when delivered by the printer, so it might be impossible to tell for certain if one was at the start, middle or end of a printing.
To be sure, in the rare book world, collectors anguish over these details too. So I am not saying it makes no difference. But it may be that the second print of C&S has two states (using that terminology) and it may be impossible to say which came (ever so) slightly earlier. Or even if that distinction is important. We might even adjust the way in which we think about some early D&D sets/books accordingly.