I clearly recall using a brand new 475 at my work place some forty years ago, on which delay timer pot was not set to zero, it was set at 0.20. I don't exactly know why, but perhaps it represented the minimum inherent delay, that would always be there when using delayed sweep, due to circuit design.
My personal 465b also has this pot set at 0.20, but I am not sure whether it was set by the manufacturer, as this scope was a used, and possibly repaired one when I acquired it. Recently, I had to do some fixing on my personal 465b, and when I reassembled, I took care to set it to 0.20, whatever it means. I don't use the delayed sweep during my home use.
Hope this helps.