Traditional European meat stock (chicken stock, beef stock, etc) is boiled for 6 to 8 hours. Supposedly (according to many answers on this website) there should be absolutely nothing left to extract from the bones and meat after simmering for that time. Yet Chinese white stock is made by boiling (not simmering, but proper boil) bones and meat over one or multiple days. I have a prepared chicken carcass that I'm planing to turn into a chicken stock. I wanted to boil the leftover bones from making stock for another day to make a white stock, but after some reading it seems to be a waste of time. I might still try it just to experiment. 
I think the hypothesis is incorrect: there are certainly Western recipes for stock that suggest cooking for 24-72 hours, such as here: http://realeverything.com/tutorial-thursday-broth-stock-bones/. Most recipes I find for Chinese white stock in English also suggest cooking only at most 4-8 hours. I have never made these long stocks but the longer cooks are claimed to continue creating more gelatin out of the bones, until the bones disintegrate under mild pressure. That certainly isn't true about bones cooked for 4ish hours, in my experience, so something is happening in the long cook, although I don't have any clear information on how significant that something is. 