"If you stick the siphon tube in crooked and it dings something, or leaves some smushy stuff in there ... Or maybe the oil pressure just goes too high and the engine blows .... Or maybe the engine blows anyway cause it runs so slow cause of all the extra back pressure from the extra oil ... Yeah! Thats the ticket! Ole Jerkin Shrimp has a new order out to overfill the oil thingy after an oil change so he will make more money and get to retire
earlier with a bigger pension! "
While they certainly shouldn't be overfilling it, one quart extra isn't going to result in any of the above disasters happening. And most of it is nonsense. Oil pressure is not related to the quantity of oil, unless it drops so low there isn't enough for the pump to pick up.