I have a 2012 Yukon XL and I had to look a while to find a used one that was rated to tow 8000 lbs. Without the trailer package (different transfer case and coolers) they were only rated at 5000 lbs.
Remember that the weight of the vehicle comes into play as well. Usually a 4WD is rated 100 -200 lbs less trailer capacity that a 2wd.
Where did you see the 7400 lb rating? I looked up the 2007 GM towing guide and it rates an 07 Yukon XL Denali AWD at 7900 lbs max towing capacity.
https://www.gm.ca/media/vehicles/com...rochure_EN.pdf
And total combined weight of 14,000 lbs. So to tow 7900 lbs your tow vehicle cannot weigh more than 6100 lbs. So you can't load 6 people, luggage and 2 dogs in the Yukon XL and still tow 7900 lbs.