A bug per MC-107749.
MC-108734
Observers don't power blocks strongly
Resolved
Duplicate
1
[Mod] redstonehelper
(Unassigned)
Confirmed
Minecraft 16w41a
Retrieved
Observers do power blocks strongly. They just don´t send enough block updates. So if you use an observer to power something through a block, you´re creating BUDs.
So the actual bug is this one:
https://bugs.mojang.com/browse/MC-108696