I've thought about this a bit more.
Look at "w" above in my post as "waste products" and then consider a bacterial culture that becomes self limiting due to production of waste. This is what happens. The wash becomes self limiting as "w" increases with time and the wash water is agitated but not changing. Therefore, the diffusion outward is slowed. If the water is running, "w" can be kept at close to zero.
Now, this does not mean that it cannot work. As I said above, there are two levels, "good enough" and "archival". Kodak and others recognize both. Your negatives should always be made archival, but prints are optional depending on use. Also, hypo eliminators and wash aids enter into this.
In the final analysis, I repeat "trust but verify".
Thanks David, the other thread like this has apparently been lost in the mist of time.