Since we don't have it yet, don't have any personal experience on this - yet.
Musk promised last year that owners would be able to have more control over firmware updates.
Evidently the latest software release may finally deliver on this promise - with the ability to request firmware updates.
Until then, when each vehicle gets a specific firmware update will appear to be completely random. We have an S 100D and X 100D, and they are almost always on different versions - often with weeks or months between new updates.
This has been an area where Tesla has long needed to make improvements - and it looks like they may be doing that in the latest software - finally...