If you use a hop bag in the boiler that prevents the hops from forming the filter bed.
If you have a hop strainer in your boiler I wouldn't bother with a hop bag.
It's not worth recirculating the wort if you don't have the hop bed on the floor of the boiler creating the filter.
The only other thing that is likely to be in your boiler is the Cold Break, it's not crucial to filter that out, people who use counterflow chillers don't filter it out, it just drops out in the fermentor.