Doubtful, and it's not arbitrary. This update replaced the kernel, thus the new build number. That Nvidia chooses to restrict their drivers' operation to a specific build number of OS X is Nvidia's choice, not Apple's.
Yes, but as I keep pointing out, if Apple had incorporated new drivers anytime since 10.9 came out this wouldn't be a problem.
By keeping 310.xx drivers in the OS whilst Windows and Nvidia have moved on to 343.xx and 347.xx drivers, Apple created this problem.
Again, for most GTX680 type cards this is no big deal.
It IS a big deal for GTX780Ti, Titan Black, GTX750, GTX960, GTX970, GTX980.
For our folks with EFI cards, they still get to the desktop to fix things. The people running unflashed cards reboot after update and get...NADA...black screen. Lots less fun for them.
Apple is basically still using the Nvidia drivers from 10.8.5 in 10.10. No new cards have been added since then.
And I don't believe that a "Security Update" has ever done this before.
The Apple apologists can stop now.