Pretty sure that VZW's approval process has nothing to do with it, since from what I understand Apple is completely responsible for the Q&A process. That was part of the agreement before Apple would even consider releasing an iPhone on Verizon's network. Same reason you don't see VZW bloatware on iOS.
I am pretty sure that the main cause of the delay is due to Apple's limited experience working with the Qualcomm baseband that is used in the CDMA version of the device. And I have read that the delay in 4.3.x is due to the fact that for whatever reason, Apple decided to wait on Qualcomm to release new device drivers for the baseband chipset.
I can only assume that the beta iOS 5 for CDMA uses the same baseband software as 4.2.8; and that they plan on having the updated drivers in hand soon enough to incorporate them into the shipping version of iOS 5.
I am getting pretty damn sick of the GSM version getting new features while the CDMA version is stuck on an old OS, though.
IF they can release iOS 5 beta with the 4.2.8 baseband then why can't they release 4.3.3 with the 4.2.8 baseband? Esp since the iOS 5 code is built upon the 4.x code base. That is a slight hole in your theory.
Verizon Q&A is involved. Verizon never lets an outside company dictate directly to them concerning policy. You either pay VZW off or you play by their rules. Been a customer with them since the very first day they started doing business in Texas and that one fact about them has been constant for over a decade.