A)the link was for an epoxy primer - which is perfect over metal
B)I've been doing body and paint for 30+ years - and as long as your metal is properly prepped, filler should ALWAYS go over bare metal.
But - what happened in your case?
I've been doing custom body,fab and paint for 20+ years, I've seen just about every possible hack work and done plenty of
for doing regular ding,using filler is ok, but I'd never skim fully stripped panels with filler without epoxy.This is my prefference since I don't want to re-do something down the road just because filler acted as a sponge and absorbed condensation and started corrosion,
evercoat primers do not stick to bare metal,I've seen it plenty with my own eyes from visiting friend's shops and have experienced peeling and blistering of that primer off bare metal that was sanded with 80 grit,it was coming off in sheets, I'm not some butcher or ignorant retard who would cut corners at every chance ,so please spare the lecture