Your mod doesn't work with OptiFine_1.16.4_HD_U_G5. If I create a new world there are no trees in the Treemendous biomes. My game version: 1.16.4-forge-35.1.10. Treemendous-1.16.4-0.4.3.
Can you fix it?

But 6 days ago a new preview version appeared and your mod now works with preview_OptiFine_1.16.4_HD_U_G6_pre1. I close the issue.

And also, the leaves and logs in your mod can't burn.