Not knowing how long particles will stay in suspension is the real fly in the ointment, for both the drain cold and drain hot camps, isn't it? For me at least, when I think of a cold oil drain, it isn't on an engine that has been idle for months, or even weeks. Rather, it is an engine that was last turned off just the previous day. Or maybe two days previous.
Also, knowing that every engine retains somewhere between 1 and 2 quarts of motor oil, sometimes more, no matter how long you leave the drain plug out, how much difference does it really make, if some of the particles that were in the oil in the crankcase, may have fell out of suspension and remain the the bottom of the sump? You still have dirty oil as soon as the fresh oil mixes with those 1-2 quarts that were still in there.
It is too bad that
@BusyLittleShop lost his source for the study that was done on this subject. Without it, or some other data, all we have are theories and opinions.