Most easily noticed for leaves. Re-create by making a resource pack that replaces one type of leaf with the correct mipmapping strategy, but not the other and place them side by side.
Left: forced to cutout | Center: built-in programmer art | right: forced to dark_cutout
Expected behavior: the center 6 blocks match the right 6 blocks
Observed behavior: the center 6 blocks match the left 6 blocks
It’s likely that this is just because no mipmapping strategies are set, so this should apply to other blocks as well. Textures are sufficiently similar where they can probably use the same strategies as their texture update counterparts.
You can load this pack above the built-in Programmer Art pack to reproduce the bug. Acacia leaves have the expected appearance, dark oak leaves have a deliberately incorrect appearance. Due to the pack not changing oak leaves, that can be used for the observed appearance.