The Bug
On Bedrock Edition beta, when you attempt to place a block below the bedrock (y=-64 in this case), it gives you a warning message about the limit below y=-64. Sadly, you don't get this message on Java Edition, which is a parity issue.
Related issues
Comments
Yeah, I didn't realize that, I'll add the vanilla-parity tag on that bug ticket since Bedrock already has that feature.
Does MC-129886 describe this issue?