I am very familiar with Dulles. As a pilot in the late '70's, I did my instrument training there.
The announcer, MentourPilot, has an accent. The airport is named after US Secretary of State John Foster Dulles - who pronounced his last name as two distinct syllables "Dul.les". Also "Front Royal" is not pronounced "Front Royale" by any of the residents in that part of Virginia.
That airport was built by the FAA to relieve air traffic at National Airport (now call Reagan). But, it was more than a decade before the FAA promoted its use by airlines. That worked out for me because, especially when the Washington DC Football team was playing, I usually had that airport to myself.