Your command center will pop up a Check Coolant message about every 13,000-15,000 miles.
The test check for Nitrites in the Coolant ( all previous Superduties used Nitrite based coolant) Your test should be 0% If somebody added the wrong coolant, You need to drain, flush and refill. If you know that nobody has every added the wrong coolant, You could skip this test.
The second test checks for Freeze Protection. New this coolant is good down to about -50°. If you have not diluted it, it will probably still be close to that kind of protection.
Third Test is for Corrision Inhibitors. Our coolant is OAT based and coats the metal with coating that prevents rust from forming with the water in the coolant. You can add the VC-12 Coolant Revitilzer which will restore the Corrision Inhibitors twice during the coolant life. Your coolant is rated to last 105,000 miles under normal use and 60,000 in severe duty.
After having paid for and used the test kits on my 2011 truck and not seeing the coolant fail. I'm inclined to follow your dealers advice, As long as nobody has been "Topping off" your coolant. If you need to add some fluid to get up to the fill mark, and you have not added it before, Just use the Coolant Revitilzer VC-12 to top off the tank. ( No more than 48oz, and not more than twice in the coolants life) Or use the pre-mix bottles of coolant from Ford.