The issue seems to the be same as it was for Iota and Sergio's DAG design, which is that there is no way to prevent double-spends on multiple branches of the DAG.
You can't just claim that there is no a way to prevent double-spends. A blockchain is a special case of a DAG and if you are right then there must be a line after which everything breaks, because (as we see in Bitcoin) the special case of a DAG works pretty well. If this line is drawn between "single branch" and "multiple branches" then how does Ethereum manage to function?