Sure that's true, but then the only way to really know what it's like to work at a company is to spend 4-12 weeks working there yourself. Some would argue that that is still not enough time to form a real opinion.
My hope with Key Values is to:
1. Look beyond what companies say about themselves and focus on the culture and values of specific engineering teams.
2. Let job-seekers access information about engineering teams sooner (ie. before the hassles of applying, completing coding challenges, white-boarding, etc).
To your point, how interviewers describe their teams can be vastly different from how it actually is. Whether you "trust" that information or not, at least you have it sooner!