It's important to remember that porn is about fantasy, not anatomy. The stats the porn guys and their studios claim aren't about measuring incorrectly...it's about adding to your sexual fantasy. Lots of people in this thread have given examples of how that fantasy is reinforced:- Big cocks on little guys, like Mandingo; tiny girls with tiny hands; forced perspective, with the guys cock practically shoved down the camera lens (a practice not unknown to members of this site).
The bottom line is that big cocks sell vids, and the bigger the claims for the cock then the better the chance for sales. That applies equally to str8 vids and gay vids. Take Jack Napier as an example, billed as 'The Biggest Dick in Porn' and yet starring in an overtly heterosexual str8 line of vids. I doubt if Mandingo and Lex Steele were selected for their Oscar winning potential either. What porn performers don't possess for real is easily corrected by slick advertising, good camerawork and sympathetic casting.
I used to chat with a porn producer/director who'd been in the industry for many years. He told me his formula when it came to casting guys. 7" = 9"; 8" = 10"; 9" = 12"; 10" = 14". Above 12", he'd never seen one.
In the days before this site became a mass attraction, I used to run a little section called the LPSG Hall of Fame. It was a league table and pics of the biggest verified cocks on the site. In those days, maybe 8 or 9 years or so ago, nobody credible here claimed to be bigger than 11 inches.
Remember the old adage guys...."Extraordinary claims require extraordinary evidence"....and remember the context of the claim and the motivations of the claimant.
cheers
Dillon