When you break or mine the copper doors, the mining speed is actually faster, compared to iron blocks, which is 15 seconds vs 25 seconds without any tools. despite they're both similarly strong to break.

Steps to Reproduce

1. Place down copper doors.
2. Break/mine them without any tools.
3. See how long it takes with a stopwatch.

Expected Result
The copper doors should break at the same time it took as iron counterparts.

Observed Result
The copper doors breaks 10 seconds faster than the iron one.

Related to MC-266152 on Java.