17 pages and I may have missed it but I didn't see any reference to SAE J2807.  This is the new towing standard:
http://www.caranddriver.com/features/that-dam-towing-test-new-sae-trailering-standards-explained-tech-dept
I have a Sequoia and using the new standard it lowered it stated capabilities from 10,000 to 7,400 lbs.  Same vehicle, same engine.  
None of the big three started using this rating system until last year, and I believe that was Dodge.  Ford started with its new F150.  Meaning you can't really compare tow ratings between the old and new 150.
My point being, the tow ratings of yesterday, which were obviously in dreamland, are now safer and consistent.  If a new truck says you can tow 10,000 lbs, you can do it safely, with air on, in the mountains.
The F250 does NOT adhere to the new standards.  Dodge and Toyota are the only two that use the standards across their entire lineup.
If the f250 met or exceeded the SAE standards why wouldn't they use it?  Fact is they don't meet the standard and the 12,000 rating in a F250 may be a pipedream.  It may be a new F150 may actually out tow some models of the f250, since the F150 was designed from the ground up to comply with the new standards.