Two worlds of the same Seeds, but completely different

1.17.40 beta, * the same Seeds!

1. The world created when the world was created with the default setting

2. when the experimental game Play-Cave&Cliff was applied

Even though the above two worlds applied the same SEEDS, they become completely different worlds!!

It's not about mountains or caves.
The structure itself becomes a completely different world!

Is this intended?

Why is it like this? Do all Bedrock users have to give up Old World?