Here is an interview from the Classic Gaming Expo 2004, the event where Steve and Billy met and played against each other.
The relevant segment is from 10:08 to around 14:30. There's a lot of interruptions and asides, but if you listen through that whole segment, Steve makes the following claims:
- He had a DK cab in his dorm in college.
- He was scoring in the 900,000s and sold the machine (he mentions the year "1990") because after encountering the killscreen multiple times, he didn't feel like there was any point in continuing.
- Years after he sold the machine, he was curious what the high score was, so he looked on the Internet as he says "about 5 years ago" (which, from the date of this interview, would be 1999) and saw the world record score. Which, at the time, was Billy's.
- Knowing that he was capable of beating Billy's score, Steve bought another machine at some point thereafter.
So, in order to doubt these claims, I would have to assume that Steve was concocting this entire story, or elements of it, out of thin air.
In order to come to that conclusion, I would need to postulate a motive for doing so. Considering that Steve was already known to be a 900K+ player by the time of this interview, I'm having a hard time imagining what that motive would be.
But I strongly suspect that the motive was not to put a fictional backstory in place for Steve, on the off chance that, one year later, a film crew would want to start shooting a documentary about his rivalry with Billy.