In the latest Java snapshot, gravel can now generate on deepslate layer below Y=0, which Bedrock doesn't have currently. This breaks parity.
Step to Reproduce
1. Go to deepslate level below Y=0, preferably in a cave.
2. Find any gravel on that level.
Expected Result
Gravel can generate below Y=0
Observed Result
No gravel generating below Y=0
lillybeacon
Gravel still doesn't generate below Y=0 yet. Based on code analysis, the gravel didn't include deepslate as a replaceable block, which is why it fails to generate.