This probably comes about because they are able to process this kind of data on a par with strictly visual images. As we've mentioned, you will read how one face blind man, Pertti, uses such things, in Chapter 8B . Of course, people mix any and all of these techniques anytime they will work. But people do discover some work best for them and develop their highest expertise in juggling those. I use clothing for example, but notice jeans very much, shirts somewhat, and shoes never at all.
People also differ in how they define the face.
Faces have boundaries, and if one can convince his traffic cop to define the face more narrowly, this leaves more data that will not be routed to the face processor and thus be utilized. One face blind man reports being able to process faces but only if seen in profile from the person's left side. But without the stubble, he cannot process the scalp at all. And quite a few of us report that short beards, hats, or sunglasses make the face seem more visible, probably because they confuse the traffic cop to some degree. I very much like the look of a one inch bandanna tying down my hair and running in a one-inch band across my forehead.