Glow Lichens generates on the surface

Summary
Glow Lichen can generate above the surface in the open. They are supposed to only generate in the caves.

Steps to Reproduce

1. Create a new world with the seed 755690896
2. Go to coords -75 95 1045
3. Check the terrain around the coast

Expected Result
No glow lichen generating on the surface in the open.

Observed Result
Glow Lichen generates on the surface in the open, regardless.

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Original Description
I found the some glow lichens that can generate on the surface, is this a bug?

Images are down here