A file can have a valid header and still contain a value that the target type rejects. ABORT_STATEMENT, the default, leaves the statement's load unapplied when a row fails. CONTINUE keeps valid rows and reports rejected ones. SKIP_FILE rejects the entire affected file, including its otherwise valid rows.
Use VALIDATION_MODE='RETURN_ERRORS' before a load when you need to inspect bad records without adding rows. Validation and loading answer different questions: a file can be readable while containing values the business should reject. After a load, inspect the target and load history together. A completed COPY is not evidence that every input row arrived. In this local account, error rows and history come from the simulated files, and an aborted load rolls back every row attempted by that statement.