New locking behavior?

According to my update history nothing has changed on my Windows 10 (Build 10586.104) machine since 2/10. Normally my machine is always on; while it blanks its screens after 15 minutes, it never hibernates or locks itself (let's pretend there are compelling non-lazy reasons for this). Yesterday it started displaying its lock screen instead of its desktop when poked after it has blanked.

1. Is Microsoft pushing hidden updates? (This answer had better be yes, I'm not ready for non-deterministic behavior from my computers!)

2. How can I return the machine to its previous state? Is the "Do not display the lock screen" local group policy the appropriate method? It seems like there should be a more accessible mechanism for controlling that behavior.

I assumed that this was some change Microsoft pushed recently, I know they've been mucking around with seeding advertising into normal usage -- but casual searching hasn't turned up anyone else with the same recent complaint.

Appreciate the help!