Entering a Nether portal may send you below a portal

When you create and enter a portal in the Nether, and a new portal in the Overworld is created on top of a tree, entering it will send you below the portal in the Overworld but not inside of it.

This relates to MCPE-28765 but isn't really the same. Note that the issue is really hard to reproduce because the game randomly chooses a position of a portal to be created, if the exact position is obstructed.

I'm reporting this on behalf of my friend. While I tried to reproduce this separately, I wasn't lucky enough with the RNG.

Steps to reproduce:

1. Create a new world with seed -725457214.
2. Create a nether portal at somewhere near the initial spawn. Then enter it.
3. /tp to 196, 79, 63 in the Nether. You'll teleport into Netherrack.
4. Break blocks to get some space.
5. Create a nether portal at 196, 79, 63 - 199, 83, 63, then enter it. Depending on the RNG, a new portal may be created on top of a tree in a swampland.
6. When that happens, players who enter the portal will show up in water below the tree instead of the portal.

Here's a video showing the issue:
http://starlight.sakage.jp/~nimms/mp4/Minecraft_201908140541.mp4