I didn't worry about the edges, as it would take a very long time for the corrosion to progress that way on sheet metal. Didn't worry about the shavings, either, just more of the usual grit at the bottom of the door.
Though if I have a dab of paint or grease handy I'd use it.
As the former owner of a metal workshop I think I'm aware of that little detail :) Especially fun when welding it without fancy processes. The speed with which that top layer oxidizes is uncanny, you can actually see it happening under a microscope.
I've seen tiny little holes in sheetmetal cause enormous trouble in no time because it causes the paint to blister, lifts it up and then exposes a much larger area, this is an exponential process, with ever new bit exposed an even larger surface becomes active in the process because the edge length keeps increasing.
MB had an interesting mishap when they switched paint processes, it caused absolutely miniscule holes in the paint, the result was entire doors rotted out in under 3 years, resulting in massive recalls. Once rust has a hold on something if unchecked it will progress rapidly.
Basically you're right, but I didn't have any trouble over it. The holes let the water out and allowed the metal to dry. This was drastically less of a problem than having the water sit in there. Even worse was the mud that accumulates in the bottom of the door would stay damp, pressing the moisture against the metal.
Holes not only let the water drip out, but help to dry out the metal.
I notice dramatic differences in rust on metal where it can dry out vs where it can't.
https://www.wileymetal.com/aluminum-corrosion-why-it-happens...
I didn't worry about the edges, as it would take a very long time for the corrosion to progress that way on sheet metal. Didn't worry about the shavings, either, just more of the usual grit at the bottom of the door.
Though if I have a dab of paint or grease handy I'd use it.