The extra leaves don't get correctly lit with Complementary Unbound shaders:

Minecraft 1.21 with Fabric, Sodium, Indium and all those usual mods.

Some types of leaves are not illuminated correctly.
Minecraft 1.20.1 with Fabric, Sodium, Indium, Complementary Unbound shaders.
As you can see from the screenshot, the standard oak leaves, coniferous leaves and others does not work correctly, but Pine leaves (Regions Unexplored) works correctly. At the same time, Rubeus Tree (Better Nether) works 50/50 at the same time.
Screenshots taken with High (Default) Complementary Unbound shaders settings

Problem with Complementary Unbound shaders setting:
Performance Settings -> Shadow Sample Quality
OFF - OK
Very Low - Doesn't work
Low - Doesn't work
Medium - Doesn't work
High - OK
Very High - OK
Ultra - OK

This is not really something I can fix here, since this is just a resourcepack.
I might get in contact with Emin (the Complementary author) to hopefully improve the leaf shading on the shaderpack side.

This is what I got:

You just need to go to Shader Settings and change the profile to "Very High" or "Ultra".

Or instead get more specific and go Shader Settings -> Performance Settings -> Real-Time Shadows -> set it to "High" or above.