Do I get you right that you don't have any problems with the technical content, but are unhappy about the style?
No, I'm unhappy with both, my suggestions go in both directions.
The main technical concern is that querying is not explained on it, it's explained on the "details page".
More in concrete, if you add "In PostgreSQL, a table can inherit from zero or more other tables, and a query can reference either all rows of a table or all rows of a table plus all of its descendant tables. The latter behavior is the default." should be a "complete" explanation of the feature.
I think a tutorial is free to use sloppier language, but then that's just my opinion.
