Smoke is a colloid. The reason one dries meats (including fish) that has been cured for smoking is that the water-soluble proteins that have been pulled to the surface of the meat will form a sticky layer (called a pellicle) once dry that allows the particulates in smoke to adhere evenly resulting in a product that is, visually, evenly smoked. Not to do so often results in a splotchy uneven appearance--it can look like soot was smeared over the meat surface here and there--that is rather unappetizing.
Prior pellicle formation is critical in cold-smoked foods (like bacon and salmon) because the smoking chamber's temp is maintained low. Without adequate heat or substantial airflow to dry the surface before smoking commences smoke deposits are frequently uneven from very early on (because there has been not enough time in the chamber for surface moisture to dry) and there is little one can do post facto to remedy the situation.
Hot-smoking provides enough heat to dry a surface but it is still recommended to allow pellicle formation prior to smoking of cured meats (again, bacon or salmon, e.g.) because of all the surface proteins and the barrier excess moisture provides to even smoke particle adherence. It can be a good idea for pastrami but is not as important because of surface differences. It is not necessary for unbrined meat such as butt and offers no advantage. For brined butt (cut and cured as for buckboard bacon) it obviously would be in order.
I'm not sure that there is really much debate as to when to put meat into the cooker. With the relatively high cook temps we use in the smoker (as opposed to cold-smoking temps) it is simply a matter of personal preference. I put all meats that will be cooked thoroughly (i.e., to barbecue finish temps) directly into the cooker just after rubbing and I pull them from the fridge to apply the rub just after lighting coals for a Minion start. For fowl and meats that will be cooked to lower internals (fresh ham, rib roasts, sirloin tip roasts, whole pork loins, turkeys, et al.) I pull from the fridge earlier and allow to come to room temp. These items--which I cook with a standard method start-up in the WSM or kettle--I cook at higher temps and do not want to drag the cook temp down inordinately by adding them cold-from-the-fridge to the cooker.
