Silk shattering is caused by adding mineral salts to the material, to make it heavier in a time when silk was sold by weight. So not all silks are affected: usually satins and taffetas (which make nice rustling sounds) and even then the better quality silks weren't affected. Lining silks are lighter and weren't affected by these practices and so don't usually shatter. They can be affected by other age and storage related issues though, like dry rot, mildew and mould. I've written some blog pieces on these issues if you'd like to know more.
You're right though: many Edwardian silk linings deteriorate, but so do those from the '30s.
I vote '30s for this lovely piece. Here's a pic of one of my (now sold) opera coats, which has a similar shape
View attachment 77863 . I still believe that yours was likely shortened.