Only reason I advocate those coating for my method is because a lot of coating failures have happened because the pores of the clearcoat heat up and oil from the polish are deposited in. So anytime the car gets heated up again such as sitting in the sun, the oil starts becoming exposed to the coating, resulting in early coating failure.
So, for me it's better to be safe than sorry and just overdo it. I also spray eraser on right after I finish polishing the specific section, when the pores of the clear are still open.