The X-30 was still exo-atmospheric. I have read about hypersonic, non-ballistic missiles but they have not hit the 5k mph that the article is talking about. I do believe that the theoretical limit of scramjet was Mach 8 as you stated but once again, these are for the upper reaches of the atmo since the air density is conducive to such speed.
Well, we were going for a LOT more than Mach 8. And part of the X-30 was that it had to fly IN the atmosphere for a long, long time.