Actually, if we set aside the specifics of the process, all we have is conjecture and anecdotes, which is hardly factual and even less credible. Conclusions like this are then based purely on opinion and rhetoric.
Actually, there is a long, well-documented history of outlier users who either have remarkably bad luck, or are otherwise remarkably astute at finding only defective Apple products, and then repeatedly exchanging and exchanging a product that apparently doesn't meet their expectations or needs, without considering the possibility that maybe a different product from another manufacturer would suit their needs better.
There is a saying for this: the definition of insanity is doing the exact same thing over and over again, expecting a different result.
Are these people really getting 5, 10, 15 or more defective iPhones in a row? I don't know because I'm not witnessing it. But the fact that after exchange number 4, 9, 14 or greater, the person still hasn't' seen fit to either wait for another production batch or go with a different product entirely is quite telling.
If that were true, Apple could've easily gone with molded plastic, which is markedly cheaper.
When one has been drinking a particular flavor of Kool-Aid for a long time, and suddenly finds themselves committing to a different flavor, they will often try really hard to convince themselves that the old flavor was sour, anyway.