Science? Not exactly. It comes down to the state of cleanliness of the pipe. I've bought from dealers and individuals, on eBay and through private sales. Regardless of the source I've always needed to take the pipe well beyond the level of cleaning that it was at when I bought it. A dealer can only put so much effort into a pipe before the amount of labor involved costs more than the pipe will bring. Private parties often send the pipe without any serious cleaning, possibly with the expectation that I'll clean it to my own satisfaction. I'll put some hours, or even days, into bringing a pipe back to a neutral state. Dealers and private sellers aren't going to do that.
One of the areas that doesn't get nearly enough attention is the mortise. Even when a seller has done a reasonably good job with the shank airway and stem airway, the mortise may still have significant deposits, and those deposits can contribute to a pipe tasting sour.
There is a lot of information on cleaning pipes, including S/A treatments, retorts, ozone, and cleaning regimens. Unless the pipe has been badly abused or smoked with some sort of strongly ghosting tobaccos, and sometimes even then, with patience and elbow grease it can be returned to a neutral or near neutral condition.