Tree growth can make logs trigger obervers
If there are some observers face to logs, and tree grow near it, the observer can be triggered.
step to reproduce:
1. build it:

2. bonemeal the sapling
3. notice the observer is triggered

expected behaviour: the tree growth should not trigger the observer, as no block is changed in front of it.
I have tested jungle, oak, acacia and spruce sapling, and they are affected, too.