These last 2 posts are false, OP.
It’s not the tires and wheels increasing the capacity unless Ford “chose” to add higher rated tires to the 20s.
Actually in general if the tire OD is the same (unless the 20s are notably taller), the greater the rim diameter, the lesser the sidewall height and the lower the load rating.
And besides people are confusing gvwr, aka payload, with tow rating that is increasing the gcvwr considerably without a large or any payload increase.
My “guess” is the 2klb tow increase is from lower gearing and may have mis-read or it misprinted.