Thank you for these links! Yeah, I would agree that it is not a normed tool, and the creator even admits that it is biased towards technical texts in lieu of "classics". In addition, vocabulary is the only decisive factor, rather than grammar and semantics (perhaps why I consistently score in the 140s on this website as my WISC-V Vocabulary was 17).
I have indeed known about these formulae for some time in addition to the website I linked. For reference purposes, many of my essays that I have completed in the past twelve months have scored anywhere from a 13.5 to 18.1 grade level in Gunning fog and 10.3 to 15.1 grade level in Flesch–Kincaid. I am awaiting for the ACT TIR for a copy of my essay to determine where it scales in these algorithms as well, but I do know it scored at the 96th percentile nationally.
