Yes, we know for a fact JS made hundreds of attempts over many months.
And yes, JS has nowhere near the experience playing 14.1 against masters like Greenleaf.
And yes, JS is capable of running 600+: after hundreds of tries, over many months, with artificially perfect conditions. Willie walked into strange room and did it.
There was no fluke to Mosconi's run. Over the years, numerous people here have reported watching him in person and saying he was far above anyone else when it came to playing 14.1. All saw 100 ball runs, almost on demand. He ran balls like water. Most people, that know anything about 14.1, acknowledge that given the slightest incentive he could have run 800 or more.
JS has s zero chance or walking into a strange room, taking two racks of practice, and running 500+.
Lou Figueroa