I am leaving in Cyprus where there is an abundant of feral cats. Over the years I have taken care of dozens of sick, injured or hungry ones. When comes to taming, and without disagreeing with what you wrote, I want to add that their individual "character" plays also a great deal in taming.

Last year 3 siblings, about 2 months old found their way to my backyard. In a months time two of those were running behind me and purring every time I touched them. The third one, Pepita, a gray female one, even today is very shy and always avoids personal contact with us!