Quite frankly this all a bunch of guessing and speculation. Generally, the critique scales used have assigned a value to four general, widely accepted, criteria and a summary. The number 100 was more than likely chosen not because it relates to any existing scale totally unrelated to cigars but for two reasons. First 100 is a number allowing for minor variations in scoring, 85 vs 84. You could use a 10-point system and allow for ratings in the 10th like 8.5 but that makes it harder to distribute across categories. The second reason is 100 equals perfection. Something most people see as the pinnacle. Everyone wants 100% on their tests. Everyone wants 100% of the vote, except Democrats who seems to think you can have more votes than voters, but that is an argument for another time and another thread.
As for how many get rated at 90, that should be totally independent of any rating site. We are not pushing cigars into a bell curve where only so many get in the 90 club. Cigars should be rated on a standalone basis, on their own merit.
The issue in comparing cigar ratings is greatly compounded by introducing humans into the equation. Humans bring problems. We walk into a cigar review with too many preconceived notions. We like this wrapper, or this manufacture, we like more medium than full. We like robustos more than perfectos. These notions are already adding or subtracting points. Even in the case of a blind review, people who like lighter cigars see a broadleaf wrapper and are already thinking they may not like this one. I recently ran a critique where the reviewer gave it a significantly lower rating, not because it was a bad cigar, but because it wasn't in his preferred profile.
Now I will agree that people who may rate a cigar on the much lower end of the scale, say in the 70's, as mentioned, might be somewhat hesitant in posting that score. Again, welcome humans.