From a criminal investigation and prosecution standpoint, so what? The fact that Congress has the impeachment power does not mean Congress has the criminal investigating and prosecution power. See Article II. Further, the president has the power to remove officers that haven't been impeached.
FWIW, Congress can impeach and remove judges too - the executive can't do that.
Read the sited text.
Regarding an Officer of the U.S., ONLY Congress may impeach AND remove. “Impeach” means “accusation” which comes as a result of investigation based on reasonable suspicion or probable cause. The executive branch is not authorized to do this regarding an Officer of the U.S. The executive branch may pursue crimes done by lower-level federal employees but not Officers.