When you create nether portal in overworld it spawns in nether incorrect regarding chunks, the position of the portal in the chunk does not match in two dimensions.
What I expected to happen was...:
The position of the nether portal in the chunk must match in two dimensions.
What actually happened was...:
The position of the nether portal in the chunk does not match in two dimensions.
Steps to Reproduce:
1. Press F3+G
2. Build nether portal in overworld
3. Enter the portal
4. See portal position in chunk
The overworld-nether ratio is 8:1, 1 block in the nether is 8 blocks in the overworld. That too goes for portal spawning coordinates, along with the portal having an area to spawn in if the exact coordinates are not valid portal spawn coordinates (eg if it would be in a wall, it might move some blocks over to spawn in a cave).
All of this is by design, and all of that on their own is already enough to make it's in-chunk position different, let alone combined.