I know so many will argue otherwise, but I once had the opportunity to work parade and crowd control for the 25th Anniversary Parade. I was so ready for the question. You know, because it is the now legendary NUMBER ONE question guests ask and guess what? I got it a total of ZERO times. Not once. Back then I also got to shadow and be with the cast of the Jungle Cruise for a day, Again... total goose egg. Now I have had other castmember tell me they get it ALL the time but the ones I know and trust, the ones I am friends with, they agree, this really is not a question that is asked.
Turns out this was once part of the Tradition's class. It was a fictional scenario, and the point of the scenario was to read the guests, "what were they really asking". In this scenario, the guest means when does it reach the part of the parade route we are standing at. Also of note, I do not think the MK's parade has EVER been called the 3 o'clock parade. It has always had a proper name. Also, WDW has always been a world destination, not a regional attraction. So while the cast may come to know the parade is always at 3pm, and thus cast call it the 3 oclock parade, the average guest are not like you and me and are not familiar enough with the operations of the park to do the same. They are looking things up, the showtimes guide have never called it, the 3 o'clock parade. Nor will it be listed at the 2 o'clock parade. Just my take.