Since i see a lot of conspiracy theories i would like to mention another one, based on a real incident that happened in the early 90's at boscombe down, England. To cut a long story short, one night a mysterious plane landed and immediatelly was covered with trapoline (i guess this is a special sheet). One man who observed the airplane , stated it looked like the the YF-23. The story goes on by saying that Northrop participated in the ATF contest in order to take money for a new supersonic aircraft. The YF-23 was just a cover. After all, during that ATF contest, the YF-23 wasn't tested as hard as the YF-22. the author went on by saying that bcz the YF-23 was resembling that mysterious airplane, it was natural to posses greater speed potential than the YF-22.
Anyway, bcz i don't remember the story well, and i may have spoiled it, anyone who likes a little conspiracy, would google for Boscombe Down.