I doubt they could have designed, tested and produced this type of fix in 22 days. People calling for a recall are kind of arguing against their own logic. They want Apple to rush out a design change and apparently skip all the testing (durability, RF considerations) while claiming the lack of testing caused the original problem. I would guess durability is a bigger concern than RF. The outer edge of the phone gets the most abuse. A thin non-conductive coating could chip or wear in an unpleasant way. The bumper case is a good enough solution for now. The only other alternative is to stop selling the iPhone for 2-3 months or however long it takes to make a design change and produce enough units to do a recall. That's going to upset a lot more people than an extra dropped call here and there I bet.