So, as far as I'm aware, this is a bug.
I've never noticed this until now, and its kinda annoying
Below is a GIF of the issue (in 20w12a)
[media]
MC-175507
Dispensers, Droppers, and Noteblocks can be detected by Observers when powered and depowered
Resolved
Works As Intended
0
This is intended. These blocks have a block state for their powered status, and observers will watch for the change in that state