Steps to Reproduce:
1. Go to The End
2. Build End Portal in the middle of The End
3. Jump in

Observed Results:
The end credits will play without killing the Ender Dragon.

Expected Results:
Should lead to Overworld without end credits, or not work at all, due to having to kill the dragon or get killed to return to the Overworld.

Notes: Found this in January 2019 and it has consistently occured since discovered. It currently occurs in v1.16.201.