Except it doesn't work in the way the myths portrayed.
In fact it doesn't stop an arrow .Theres multiple tests done on this to disprove it.(I did write a very long explanation out it just looked like preaching.
) basically Monoglian bow verses Mongolian armour and clothing. Head on at 30m-40m bow wins every time No silk in the wound other than the edge of the hole being dragged in by friction on the arrow shaft.The arrows at 30m are getting well over 30cm penetration .On a body in armour there's simply not enough loose fabric or room for the material to travel even if it could these are more than fatal depths of penetration.
The myth has more than likely a basis in truth .But it simply had to be an arrow which had spent a great deal of it's energy before impact ,enough loose silk fabric,and a shallow wound. Similar effect with dueling distance and power charge play a part plus these myths never mention those who were wear silk and were turned into a colander.
The reality is silk has very good thermal properties and it gets bloody cold out that way and on occasion baking hot.Silk is pretty good in both extremes.
As mentioned silk is and was a luxury item .The odds of every nomad on the steppe having silk are pretty low.