As discussed in the video (https://www.youtube.com/watch?v=k20yLpW8-xU&t=782s), create or alter enables declarative table definitions and updates.
The video states it is in private preview. How can I get access? When will it be available to all accounts?
Snowflake has a policy of not promising dates. So for any question "when is the ____ feature currently in private preview going into public preview?" - the answer is "we don't know, but hopefully soon".
The best place to monitor to check what comes into public preview is: https://docs.snowflake.com/en/release-notes/new-features