Specific world the height isn't 320 height limit when Caves & Cliffs feature is turned on

Summary:

My world is still max height is 256 in overworld, not 320. I am using newest beta version and caves & cliffs is turned on.

Step to reproduce:

1. Open the world was created before 1.16.220.50 (by enabling caves and cliffs experimental features)
2. Using this commands: /setblock ~ 255 ~ dirt
3. Place 2 blocks in above

Observed results:

This world height isn't increased to 320.

Expected results:

The world height should be increased to 320 in overworld when caves and cliffs is turned on.

Warning on this changelogs:

The blending between the old generation and the new generation in this beta is not finalized yet. We want to make sure we respect players' old worlds being upgraded to the new world generation and are working hard to improve the biome blending for the full Caves and Cliffs release!

https://feedback.minecraft.net/hc/en-us/articles/360057402352-Minecraft-Beta-1-16-220-50-Xbox-One-Windows-10-Android-