Minecraft doesn't correctly unload textures in the atlas

Steps to Reproduce:

1. Open a Minecraft world
2. Load this resource pack : https://www.planetminecraft.com/texture-pack/spherical-vanilla/
3. Press F3+S to print the texture atlas
4. Unload the previously loaded resource pack
5. Reprint texture atlas
6. Compare texture atlas, and see that certain textures are still present.

Observed Results:
Some loaded resource pack textures are still present (even though they're not supposed to be loaded)

Expected Results:
The resource pack textures are all unloaded