We don't know what is being tested or if anything is being tested.
In the case of 5.9.902 the test lasted one day. My guess on that one was that they tried a new technique by sending 5.9.901 out to the people who reported problems so they had a pretty good idea that 5.9.902 would be OK.
The documentation for 5.9.902 and statement that you could download it was posted on the Verizon website 3.5 weeks after it was released and pushed.
There is insufficient information for a valid conclusion of the status of anything ... and always will be.