To each it's own. Probably diffusion is adequate. These washers were invented to sell. 2 of the 3 washers I have came to me for 5 cents on the dollar, at least a decade old, took me hours to get the protective film off the plexiglass dividers. Water here is under pressure, air dissolves in the water, when it exits the tap the air comes out of solution. Very tiny air bells collect on the surface of the paper, preventing salts in the paper from being dissolved in the wash water. If you run 3 gallons per minute or faster you can get away with it. Slower I have issues.
All commercial color processing works with these pumps. Counter current washing final tank flows into 2nd to last, 2nd to last flows into 3rd to last.
This is how critical solvent cleaning works.
I'm not going to fool around with Counter current washers. I just use recirculation for a period, siphon off the water refill rapidly, run the pump again, repeat until desired residual fix is reached.
It's only logical.