I have to agree. I don't think there is anything wrong. I t may be more a case of you getting familiar with how your truck responds under various conditions.
The 4.7 is a small engine, and if the load is enough to make it lug a little, the computer will quickly respond by telling the trans to down shift.
If you are concerned, I will recommend taking to the dealer....with the boat in tow....and have a technician take it for a drive to evaluate what it's doing under the conditions that concern you.
Either way, keep us posted as how you make out.