Placing end crystals on the exit portal in the end does nothing, as seen on the attached screenshot.
This world was started in a snapshot, but quite some time after end crystal crafting was added.
I also hollowed out one of the obsidian pillars.
Edit: Found the issue. ExitPortalLocation in level.dat -> DimensionData -> 1 -> DragonFight was saved incorrectly. Y was saved as 56 when in fact 57 is correct. Not sure if that was only an issue in the snapshots or if it still persists.
Complete world was too big, but here is the end.