This is not a lightweight update, weighing in at 285MB. Heck, your distant relative who recently had a C-section, gave birth to something smaller. The update improves the performance of the camera, brings a fix for visual voicemail, and adds compatibility to the ISIS mobile payment system.
Motorola likes to do these soak tests because if something goes wrong, a smaller number of phones are bricked. Seriously though, by keeping the update isolated to a smaller number, it is easier to find and correct any mistakes, and it also means that Motorola's financial risk might be lower than if everyone's DROID were to be updated at the same time. Not that we expect any mistakes. And once the soak test is out of the way with a passing score, those of you not on the Motorola Feedback Network can start to receive Android 4.4.4.