All giant taiga trees and giant jungle trees have one log block in the northwest corner (negative X and negative Z) that is slightly higher than the rest of the logs on the tree. I believe the tree should either have a random raised corner or no raised corners, but the constant raised northwest one is horrifying to look at and seems a lot like a bug.
I've attached a screenshot with a seed that spawns you near a mega taiga so that you can see the issue. I've tested multiple seeds, so it isn't a weird part of this specific seed. This also includes giant taiga trees and giant jungle trees grown with bonemeal.