Villagers and vindicators can open copper doors as if they were wooden doors.
How to reproduce:
Use the 1.21 experimental pack
Make an enclosed space with only one exit
Place a copper door closing that exit
Spawn a villager inside the enclosed space
The villager will open and close the door without any issue at all.
Expected behavior:
The villager should not be able to open the copper door, as they should only be able to open wooden doors.
Sidenote: this would even be useful as copper doors would be the first door that can be opened by players but not by villagers.
Related issues
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Comments

Per the changelog, copper doors are supposed to be like wooden doors, not iron doors.
This makes a lot of sense as players too can open copper doors by hand.