You theoretically need the second lower pot for that air pocket, so the return never gets blocked, because perlite floats 100% Fact. when you feed (my setup) the bottom layer will fill slightly upto the return feed line, while water continues to flow out. having just the sock will not prevent the issue. You may get away with it, but if small fragments of perlite have gotten to the return outlet that will severely slow your gravity return. (as to why one pot is taking longer to flow.) You could turn your tap off take the return hose of the base of the pot, ad clean it out a little, but without knowing where the exact blockage is will be a guess, and likely happen again. So the second pot in my system does serve it's purpose for many reasons.
Get the pot soks they will save you sooooo much hassle. I NEVER get a blockage, and rarely see any perlite come through my system bigger than the size of a dick hole. which just floats anyway.
always happy to help man you are doing great!