How could you get data? Basically he just went through every feature of the face and assigned a 0-2 positive score if you have the ideal structure, and a 1-3 negative score of you have the unideal structure.
The fact that several "incels" were in the top percent is to be expected. Every incel community is always highly populated by very attractive men who come here for their own reasons. Some are lazy and never made an effort with women. Some are "too anxious". Some just want a self esteem boost.
If you ever saw people's pictures on /r9k/ or PSL sites or even here in the rating thread you'd know we always get some extremely good looking people here.
It's pretty much impossible to score highly on that test and be physically unattractive. Scoring highly if done legitimately basically proves you have no identifiable physical flaws.
Percentiles could be standardized using our responses for the lower range. Eg. I have the record low score so it probably doesn't go lower for most people than -20. And on the high end you can score some male models. Pretty sure they'll land in the 5-10 positive range which then establishes the top percentile.