The bug
When copper golems naturally age, they take time to transition to each oxidation stage. After reaching oxidized, there is one final time delay before the golem becomes a statue. However, when a copper golem is created already oxidized, this time delay is skipped and the golem becomes a statue instantly. This differs from the behavior in Java Edition.
How to reproduce
Place an oxidized copper block
Place a carved pumpkin on it
Break the chest
Wait a few seconds
Expected behavior
The golem should take another few hours before it turns into a statue
Observed behavior
The golem turns into a statue almost right away
In prerelease 2, Java made oxidized copper golems able to turn to statues right away, so this is likely WAI