Xan, I am probably wrong, but I think GZ had to file because given the size and disposition of GZ the CC deal has a marked material effect on the company and the PPS (if only for a day :).
Such examples as 3M or Sony may not have to as they are well established companies and those deals would have a limited material effect on the company.
If I am wrong or missing something else, I'm sure someone will point it out and we both will learn. :)
Doing the walk around on the rocket as we speak. Close doors in 2 hours 9 min!!