According to the wiki* and comments by moderators here in other posts, Obsidian should only be mined with Diamond and Netherite pickaxes

It is also being mined faster than the time it says in the wiki that it should be destroyed

Couldn't find any post related using the search tool, apologies if this was already posted. Might relate to MC-173833

*I am aware the wiki is not an official source of information, but it's the best reference non-coder players have of how the game should behave