Well, since the devices don;t all exhibit this behavior, and many of them can't even be made to ground out, I;d call it a failing of manufactruing the coating proerly as it is applied to the metal rim (which shouldbe non-conductive to begin with).
I happen to have a significant engineering backing, heavy in both electronics, magnetics, and RF. I'm not an antenna engineer, but I can do the calculus and understand the physics involved very well.
The release was from anandtech, and was a well done fairly scientific, repeated multiple times on multiple devices, and using fairly professional equipment and both lab and field testing methods. It's a preliminary study, but a very competent start to a larger scale analysis. They're a well trusted source.
19db is bad, top of the curve bad, but the average is over 12 and the previous generation iPhone, which no one noticed, dropped 13. More so, better IS better, since usability and reliability actually means something compared to number on paper.
As for the car, every car performs better or worse depending on how you drive it. Shit, just making more right turns and fewer left turns can have as much as a 10% impact on your driving. That's not a valid analogy anyway. Better is better if there's no drawback vs the current option. A new system might have it;s own limitations and quirks, but so long as those limits are at their worst still above the options otherwise available, and the limitations and quirks do not introduce new negatives, then that is the very technical definition of better (not perfect, which all you anti-apple people think you deserve nothing less than).
I'm not pro or ant any vendor. i take no allegiances. I'll drop one product to buy another anytime there's a good reason to, and I'll always recommend the best product for a person's needs regardless of any perceived personal preference. I'm a systems analyst and solutions engineer, I have to be open to options. To some I recommend apple, to others android, and to others to stay the fuck away from smartphone entirely. I recommend widows to some, mac to others, linux/unix. IBM to some, Apple to others, though I've not found a reason to recommend dell to anyone in many many years. My interest here is stopping FUD, propogandsa, and general bullshit and hate flowing here. Wether the data anandtech has meets your requirements of scientific enough or not, fact is, no one else has ANY data, and until they have contrary data, it;s conjecture, and is to be dismissed or studied, but not commented on, and certainly not sued over, until there IS such data.