Official admission to the Union requires Congress to draft — and the president to sign — a bill called an “enabling act.” For Puerto Rico to become a state, it would need to convince Congress and the president that statehood is not only in the best interest of the Puerto Rican people, but in the best interest of the United States as a whole. The U.S. Senate and the House of Representatives would need to approve the statehood admission by a two-thirds majority vote [source: The Week].
https://people.howstuffworks.com/new-state-in-us.htm
Everything I’ve read said statehood is a simple majority vote, not 2/3. Where are you seeing the 2/3 vote?
Whoever wrote that piece has apparently never read Article IV, Section 3 of the Constitution. That lays out how new states are admitted.