I believe we simply assume that the reputation and trust built over time allows us to take the numbers as 'real enough' from that program & website.
Anyway, answering my own question: multiple results have been uploaded in the past two days and uploaded by anonymous users. Maybe tech reviewers running it with devices they received early?
https://gfxbench.com/allresults.jsp?order=date&page=1&D=Appl...
Also large developers like Adobe, Microsoft would have had retail units months ago to help with final testing.
I was trying to point out that disputing things is fine, but the whole basis of a website where benchmarks are uploaded is trust-and-reputation-over-time to the point where enough other people can re-run the same tests on their machines (one they get them) to validate the results. Heck, you might almost call that science!
Right now, there aren't additional results and you can't easily reproduce them because the machines aren't wide spread or available. But we can take the track record and reputation of the site and application and use that to value the integrity of the published benchmarks to be 'likely correct'.