I see nothing on that page (including the legendary section) that says you will need to do the zone to revered in order to unlock the second legendary. They don't even mention the second legendary.
"The Cypher of the First Ones is a very big system, which will drive a majority of outdoor content, and will be available week 1. The major goal is to incentivize exploration, though raiders should be able to ignore the system if they want to - no raid player power will be bound to it."
"Majority of the outdoor content".... "raiders should be able to ignore"