The full quote from that page is:
To be more precise, the default is for an SQL statement to be committed when it is completed, not when it is executed. A statement is completed when all of its result sets and update counts have been retrieved. In almost all cases, however, a statement is completed, and therefore committed, right after it is executed
This explains things a bit more. It shows that after a query is executed, there is some more housekeeping - the result needs to be returned to the user. Usually this doesn't take long - especially since we are dealing with update/insert/delete queries. Hence people think of commit and execute as the same thing.