You could be right. Maybe it is Vedder material. But After being in the agg industry most of my working life, I know what a ton of river gravel is worth to the retail market, compared to any old fractured 5" minus is worth off the mountain. It's just not a good business decision. Or a practical one to use as a road base. Go pile up a bunch of marbles and try to drive a toy car over it.
That said much weirder things have happened. As a truck driver I would tell a guy to pound sand if I was the first one to a new site to get to try out a new road made of river gravel.