I don't know if it's possible, but being able to cull the extra model parts for bushy leaves resource packs such as This one would be amazing and it would make bushy leaves way more performant (currently nearly halves my fps from default leaves without the pack to fast leaves with the pack). I have noticed that when I have leaves set to fast, I can still see several layers of bushy leaves behind the culled leaves. Please and thank you ^^

I'm going to give a suggestion about this topic

Most bushy leaves textures choose to use fewer extra faces (making a single face responsible for the top, north and west of the block at the same time, and making the use of a cullface unfeasible) rather than using more faces but using cullface. The reason for this is probably an erroneous view of optimization, practicality when making the model and textures or simply because textures have been made this way for a long time.

A solution to this would be to check if all 6 faces of the block are hidden and completely disable its rendering in this case. It wouldn't be a perfect culling but it would support most available textures.

If this is not possible by More Culling alone because there are many different models or for whatever reason, adding a way to resource packs to become compatible with this type of culling without the texture developers having to redo their model from scratch would be very good.

@Slooshie1
I believe I can do this. Although if I add an option to remove busy leaves it would remove all bushy leaves, not just the ones on the inside of the blocks.
For example: Vanilla Tweaks Bushy Leaves (download link) only shows the bushy leaves on the outside of the leaves when using MoreCulling since the cullface was properly setup on the model.

Sounds like your issue may be that the resource pack creator did not properly setup the cull faces for the bushy parts of the leaves.

I may still however add an option to remove all bushy leaves in case someone likes the leaves without the bushy parts. However that will be a feature for MoreCullingExtra