Portal takes player to same X,Z coordinates in Nether as were in Overworld

Steps to reproduce: see this comment

---

I make a portal in the OW at 1000 when I get to nether I'm at 1000 nether I go back through portal I'm at 8000 OW. I go back through and I'm at 8000 nether now and don't see a portal. make a new one and go through and I'm in the OW at 64000