The mystery is over. Bogdan Popa broke the news Friday on Softpedia that the release of the second and third versions of Microsoft's KB 3022345 and KB 3048043 on May 5 and 6 is related to a bug in the earlier version which "prevented computers… from getting additional updates in the future."
I reached out and received the following comment from a Microsoft spokesperson:
The re-released updates in KB3022345 and KB3048043 address an issue that was preventing some customers from getting additional updates. This builds on our commitment to deliver continual updates to create a richer experience for Windows customers.
The two patches are quite odd; KB 3048043 is a fix for screen flickering on the Metro Start screen in Windows 8.1, and KB 3022345 enables "Diagnostics Tracking Service" in Windows 7, 8.1, and Server 2012 R2.
There's a lengthy discussion of problems with DiagTrack on the Answers Forum, and a report of blue screens associated with DiagTrack in Windows 10. According to an event log on the latter, the blue screen was caused by:
Session "AutoLogger-Diagtrack-Listener" failed to start with the following error: 0xC0000035
Both are optional patches, so they're only on your PC if you manually installed them. It looks like you can uninstall KB 3022345 via Windows Update with no ill effect.