Pricey yes but so is the average high end wind breaker.
I have a Patagonia Houdini jacket and it is super light and worth it's weightin uranium.
If on a trail run I had a jacket that works like the Houdini but added more efficiency to the application of field expedient insulation; well cool.
When I trail run I am Uber minimal; a jacket like this might add to my options. But Yes you don't need special pocket to fill you shell with insulating debris.
B