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.
ArrotinoD
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.