At least for Postgres, this won't work the way the author describes.

And then by magic the results of this query will just always exist and be up-to-date. You can just query it and it’s instant;

This is not true of a materialized view, which needs to be refreshed after changes. PostgreSQL does not support incremental refresh out of the box, so you must refresh the entire view. A standard view would be "magically" up to date, as it is going to defer execution to runtime.