Copper doors and trapdoors mining speed is faster than iron counterparts

When you break or mine the copper doors and trapdoors, 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 and trapdoors.
2. Break/mine them without any tools.
3. See how long it takes with a stopwatch.

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

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