When I was roaming through a forest on my survival world, I spotted a birch tree with half of it's leaves gone, I opened chunck borders with f3+g and it turns out, the tree is in the middle of 2 chunks, this happened on another world with an oak tree but I thought nothing of it.

If you want to see this tree, go to minecraft 1.16.5, load a regular world with the seed "-435192646222254667", go to -95 ~ 345.

Sorry for the terrible birch leaves in the picture, it's an fps booster resource pack.