The structural strength of matted *hair* does not stand up well compared to it's weight.We're not talking about modern lightweight hairsprays here... just sweat and blood. Enough of that to stiffen the hair would weigh it down so that it would not stick out.
What part of DEMONSTRATED do you fail to understand. The questions you raised have not gone unasked... and unanswered all these years. These are not amatuers performing these experiments. When the dried blood and water soaked hair was supported from the back by the customary chin strap to keep the mouth closed (you do notice that the mouth is closed?), the stiff, unwashed hair, especially the traditional Jewish forelocks, did indeed stay forward.
The shroud also presents evidence that in addition to the dried blood and sweat, the hair may have been oiled or greased, as the queue (the unbraided braid) on the back of the head, seen on the dorsal image, is the only thing that is "blurry" on the Shroud. The Bible speaks of Jesus' head being anointed with oil.