Build height is 256 instead of 128 in the Nether

I expected to hit the build limit at 128 in the nether like on the Bedrock Edition 

What actually happened was

I was able to build right up to the overworld build limit, 256.

Steps to Reproduce:
1. Go into creative in the nether, fly up and through the bedrock and simply place blocks vertically until you hit the build limit.