Purely speculation on my part, but I have been wondering about the overlap days where some cars are getting one release while others are starting to get another (and a few examples of real stragglers that are weeks behind).
My speculation is that when it is your car's turn, Tesla starts queues up the latest release available at the time. However, you don't get notified about this until the update has been downloaded to the car, which can depend on various factors including your connectivity. And then there is the lag until you decide to install the update and the car has whatever connectivity it wants/needs to accomplish this. Thus a later release could be pushed to (and installed on) someone else's car before the release finishes loading to your car and you install it. Thus we see a tail on one release as it finishes getting pushed out while the next release is ramping up.
However, I remain baffled by the logic governing who gets which release. After being on .236 for about six weeks, I got .249 last week and then got .251 this week, exactly 7 days later. I haven't seen any evidence of anything disastrously wrong in .249 (in my experience or reported on the forum) needing a fix PDQ.
