You’re right - The caveat is we don’t know how many users actually fill out the hardware survey, or how representative it is of the Steam userbase as a whole.
However assuming there’s ~21 million steam users logged in on average, to get a representative sample size / 2% margin of error / 95% confidence level, I think polling logic suggests that you would “only” need some 2,401 systems to respond to the hardware survey.
I’m not Steam Scientist, but I’m guessing a helluva lot more that that opt in to the survey?