I am not gay (I know, famous last words) nor have I ever measured anyone other than myself, nor have I seen anyone erect (I think). But here is the anecdotal information on flaccid 7-foot cocks I have.
In the mid 80s, I covered the basketball beat for west coast conference university. Having seen hundreds of nude men and interviewed them nude (even some professional players) my experience is there is little difference among men up to around 6' 7" or so. Emphasis on "or so". Some appear huge, some don't. But so do guys at 5'10.
Things change at around 6'9" or so. I have never seen a "small" man at 6-9 or taller. Ever. the 7 footers all are significantly hung in a flaccid state. No question about it, at least in my sampling.
I am only 5-7 but have a number of non-sports friends who are well into the 6 foot range. My closest friend growing up is now 6-4 and is enormous. Scary thick and multiple times my size flaccid. He was huge and everyone who knew him.. knew it.
A kid who lived on my street is 6-9 (and wickedly skinny). He is hung. God bless him; not the most attractive guy but he got the girls. Not hard to imagine why.
But my college room mate who was 6-5 was remarkably average. A good friend I met later in life is 6-3 and probably larger than average.
Bottom line. Of the the tall guys or basketball players I saw, there are the normal differences. But I never saw an average hung guy of 6-9 or 6-10 or 7 feet. Compared to us normal folks, they blew away the averages (excuse the pun).
The largest I ever saw was a pro player. The guy was longer than my leg. Messed my mind up for a while; I felt ridiculous inadequate.