I think this is the first time Benter has admitted winning the Triple Trio. The only mention of it I could find just said it was suspected he had won the unclaimed prize.
One aspect that isn't mentioned, is that Benter (and Zeljko Ranogajec, mentioned at the very end) got a large edge over over punters by negotiating large discounts/rebates from the betting pools by providing such large volumes. It's easier to make a profit when you are getting (say) 10% back on your losing bets...
Disclosure: paraphrasing Sirlin http://www.sirlin.net/ptw/
https://www.scribd.com/doc/166556276/Benter
If you're interested in those two papers, the earlier paper 'Searching for Positive Returns at the Track: A Multinomial Logit Model for Handicapping Horse Races' (Bolton, Ruth N. and Randall G. Chapman) is also worth reading:
Edit: there's a 2008 version or reprint of the first paper: https://www.worldscientific.com/doi/abs/10.1142/978981281919...
I don't believe that's a paywall, just Researchgate being scummy like usual and using a citation while pretending to have a copy - all that would do is ping Benter to ask for a copy. I can't find any evidence that that conference presentation was published or that the conference proceedings as a whole were ever published.
No, he told this story decades ago, and published papers detailing his algorithms, e.g.
Benter, W. (1994).“Computer Based Horserace Handicapping and Wagering Systems: A Report.” In L. Hausch and Ziemba (eds.), Efficiency of Racetrack Betting Markets. San Diego, CA: Academic Press, pp. 183–198.
Benter, W. (2003). “Advances in the Mathematical Modeling of Horse Race Outcomes.” 12th International Conference on Gambling and Risk-Taking, Vancouver, BC, Canada (May 2003)
There are videos of him (just search youtube) presenting at conferences detailing some of his algorithms too... there are no secrets being revealed for the first time here!