That vid has popped up everywhere recently. Read the story in Sled Driver about 20 years ago.
I've always wondered if he didn't exaggerate it slightly though. I've witnessed an F-15 on radar once going over 1000 kts. "Rogue" out of WRB for a post maint hop. Started out at 500 kts at FL490. Once he got out in the warning area he accelerated at an amazing rate. My data dude and I watched as he went from 990 kts GS to +++. That's all that the software was designed for, three digits and in 10 kts increments. Above that, who knows how fast they're actually going. Heard from a center controller that worked in the 80s and he said his stuff only registered a 3 digit GS as well.
Possibly the high sectors use a different software???? IDK.