A powerhead will make detritus circulate until it is exported by the skimmer, that's the idea

In the meantime some inhabitants can feed on it.
I don't have exact measurements, but I've used socks in the past which I cleaned regularly (let's be honest, almost no one will change them out EVERY day after a while) and noticed an increase in nitrates. I think phosphates would have been increased also, but I don't trust the test kits enough to state that.
But the rise in nitrates made sense to me. Nutrient rich particles (detritus) in a high flow and oxygenated environment convert to nitrates relatively fast. Just my experiences though
There's nothing wrong with filter socks I think, I also use them. But I always use them for a short period because of the reasons above.
Leonardo