can walk outside the world when you fly above world hight

When flying above world hight and you approach the end of the world you can pass the end of world and walk on it .

What I expected to happen was that I would stop and not be able to fly out of the world .

What actually happened was that I flew out and could walk on it too.

Steps to Reproduce:
1. Fly up placing blocks until you cant place anymore .
2. Look up and fly to the end and your going to fly out .
3. This also happens in survival