A coworker has an F150 with about 160k miles. It's had one brake job at about 70k. He heard a noise that sounded like the pad wear indicator so he bought some pads, etc. on his way home that night, anticipating doing a brake job. He found the same thing you did and had to look elsewhere for his noise.

He had used a premium aftermarket pad on the first brake job. Was in disbelief.