He's right, Donald.
"Lying to Congress" is not impeachable. The President can lie his head off at the State of the Union, at press conferences, and so on. And does.
What is impeachable is suborning or committing perjury.
People who testify before Congress usually do so under oath. You remember the big stink about Dr. Rice testifying under oath. That was why it was such a big deal.
Presidents usually avoid testifying under oath the way people avoid the Plague. But if a President suborns perjury, if he instructs his subordinates to commit perjury (conspiracy) or fails to correct his subordinates' perjured testimony (accessory after the fact), that's the kind of lying to Congress that can give impeachment hearings traction.