the root reason is
use cny buy bts on exchange , people cannot buy a big amount of BTS at a same price , because the process of buy would make price increase
but use bitcny force settle bts can settle his all bitcny to BTS at settle price.
actually in the world , there is no bank , can convert all cny. it mean if all people withdraw all their cny from bank , this bank must close, and in reality never all people want to withdraw their cny at same time, so bank just need to 10-20% cny stored in center bank to case withdraw,
So to solve this problem ,there are two direction
1.limit total force settle percentage
2.reduce radio of force settle .