The latest snapshot regenerates my world from the latest release (demo)

Imagine this scenario: I create a new world in Minecraft Demo in release 1.15.2 and I play it for a while. Afterwards, I upgrade to the latest snapshot (1.16 Pre-release 2) and find that my world has reset and I have to restart from scratch.

Thankfully, I have made backups of my world, but still it is undesirable that I play this way. Please fix, I would be glad to give more information if necessary.