Basalt Columns can be over 10 blocks tall

Verification builds:
Java snapshot 20w19a - Yes

Repro Steps:

1. Create a new World in Creative mode.
2. Build a Nether Portal and enter it.
3. Locate the Basalt Deltas biome and fly around looking for Basalt Columns taller than 10 blocks.
4. Observe the issue.

Observed results:
Large Basalt Columns can be over 10 blocks tall.

Expected results:
Large Basalt Columns are 5-10 blocks tall.