You may be speaking in more candor than you know. The percentage stats,1% club included, isn't usually meaningful to men who typically aren't in a position to actually see another guy's erect penis.
Granted, it is almost taboo to refer to another man as being hung small or as being on the small size. But equally vexing to many deemed moderate in length and girth, despite push back from their partners, are scientific studies that characterize them as modest in "stature".
Men really only know the comparable stats of close friends, peers and, perhaps, athletic companions. In my case, peers and friends appeared to hang mostly the same as me.
That's my reason for saying that the percentages indicated in your graph seem understated. So it doesn't matter that most other unknown men hang differently than me. Ìt's the one's that I know personally that matter most.
Note: My reference group consists of about 15 or 20 friends, including cousins, that I've known from childhood. It also includes men who played sports and worked out at various athletic clubs.