When growing oak ( & sometimes spruce) trees that generate with leaves too close to the ground, you not only suffocate, you are stuck in the leaves until you break yourself out.
I believe that leaves from growing trees should push the player out of the way instead of trapping the player.
Possible Resolution:
Instead of making these blocks(leaf blocks) only suffocate you, make them push you out of the leaf block's boundary when you are inside them(again only for leaves from growing trees).
Can't believe this was counted as a duplicate of suffocation damage. This report was on being stuck in leaf blocks and not being pushed out of the way by growing trees like it use to be in some prior versions. How lame. It should be marked as related to MC-46765 there's a reason why I put stuck in bold and put the title as STUCK in leaf blocks from generating trees and not suffocating in leaf blocks. There is a world of difference but who cares I suppose.