There are some that believe angular crushed rock will compact tightly and limit drainage. The important thing is that the aggregate is washed to remove the fines.
Angular particles are preferred where filtration is the goal. Round particles do reach full compaction much more easily and the flow channels through the bed are more uniform and thus less likely to plug. Any debris that makes it through the front face of the rock bed will more likely make it all through. Sand filters use angular particles for depth filtration.
