Earlier quoted context omitted.
The college I most recently consulted with had to take a homeschool "transcript" that can literally be a signed paper from the parent handwritten with nothing to back it up. It's astounding. I don't know if that's just because that particular state doesn't have very strict rules around homeschooling, or if that's standard; I just haven't done the research.
How else do you think a transcript should work? What makes you think a random private school transcript has anything else backing it up? Presumably the students are also applying with ACT/SAT scores in hand, which do have an established meaning.
And ACT/SAT has become optional since covid for most institutions.