Red giant mushrooms use one wrong new additional block, in the very middle, the uppermost block.
In the back you can see a red giant mushroom planted in 1.13, in the foreground a red giant mushroom, planted in the current 1.14 prerelease 5.

Back in the 1.13 snapshots, I created a resource pack addon with which all blockstates of red and brown giant mushrooms can be displayed separately, for mapmakers to create additional (usually unused) blocks for their maps or SMP with a custom resource pack.
Showcase/short explanation video: https://www.youtube.com/watch?v=al5L9e9eDHU

Upon testing the updated version for upcoming 1.14, I noticed that the current red giant mushroom contains a wrong new additional blockstate block.

Previously, the block used had these blockstates:

down: false
east: false
north: false
south: false
up: true
>>>west: true<<<

Now that block uses these blockstates:

down: false
east: false
north: false
south: false
up: true
>>>west: false<<<

The west-direction was changed from true to false.

As a mod pointed out, the initial center texture was a wrong one, iirc I noticed that myself back when I created the pack, but assumed that it was intended, to only use up 16 blockstates and not 17 - or rather back then meta data values.

Thus I believe it may be an old metadata remnant due to the previous block limitation.

Just want to make sure that this is now WaI, so I can change the pack accordingly.

Thank you!