End portal blocks can be broken in creative mode

The only blocks you can't destroy in creative mode are all types of Air, Water, Lava.

Also all types of Command Blocks and Structure Blocks but only if you're not opped or singleplayer cheats are disabled.

I'am not sure that this is a bug.

Thank you for your report!
However, this issue is Working as Intended.

The report you have submitted is working as intended, mechanics of the game may change between updates.
Things such as graphics, sounds, world creation, biomes, redstone, villagers, and animals may not work the same in current versions.

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