AS for transferring weight to the front end, you don't really need to with a pickup, as long as the rear axle can handle the load.
I don't agree. That might be the case with a heavy 1 ton dually that isn't affected much by 1k+ tongue weight, but restoring front axle weight is important in lighter vehicles. Control issues aren't usually due to the ass being too heavy, it's from the steer axle being too light.
10% to 15% is just for planning reasons. Many boats tow very well with only 5% of the weight on the hitch. I once picked up the hitch of a 5,000 pound trailer by myself, I was only 11 years old, and it was not more than about 75 pounds.
Towing a boat is a totally different beast. The axles are further back and centered under the majority of the weight. The same principles for tongue weight don't apply.