They don't corroborate what can be seen, and the conditions under which their length of the game was recorded by those GAFers isn't clear. If it is a estimate them verifiable footage is more trustworthy. If it is a stopwatch, active measurement then it becomes significantly more credible.
If you look at it from a logical perspective, they very well could.
Add in a harder difficulty - X amount of extra time
Add in further exploration and exposition - X amount of extra time
Add in all the readable articles, posters etc - X amount of time
Add in the collectible items and moveables - X amount of extra time
Add in differences in combat and gameplay approach - X amount of time
Add in potentially attempting specific trophy tasks - X amount of time
And so on.