I can confirm that this is indeed a bug. This feature was working as intended in 1.11 release, but started doing this in 1.11.1 and still does so in 1.11.2. I was trying to name stacks for an item sorter, and much to my surprise... not currently possible due to this bug. Although, I am pretty sure it still works in creative mode. Just not in survival.
How was it a "bug" at all? Observer Blocks should be able to detect each other changing states.
The actual bug is that they are not doing so.