Minecraft Education .mcworld exports fail to import into Bedrock

I built a flat world city in Minecraft Education over 3 years.

Minecraft Education version: 1.21.133
Minecraft Bedrock version: 26.33
Platform: Windows

I exported the world as a .mcworld file and tried importing it into Minecraft Bedrock, but it always says "World import failed".

The world is only 13.6 MB and was manually built. I removed add-ons/resource packs and tried exporting again, but the issue remains.

Copying the extracted world folder into the Bedrock minecraftWorlds folder also does not make the world appear.

There should be a clearer error message or better compatibility between Minecraft Education exports and Bedrock.