I feel like some of the things on your list are rather arbitrary and a very surface-level, stereotype-based explanation of why this happens. I believe it has more to do with hormones, genetics, and sometimes even sheer luck…my birth mother, my aunt, and me were not lucky enough to be part of the group of females that recovered. People who go through lots of trauma at a young age (whether male or female) are also way less likely to recover from their stuttering.