I find that no matter what time I check in, my requets are always ignored and clearly never even viewed by anyone. It's become a running joke with me.
My recent stay at WL was predictably very typical of my luck. I paid for a courtyard view, and requested a balcony (a non-ground floor room). I was traveling solo, and didn't want ground floor, partly for safety reasons, and partly for privacy. A balcony sounds like a simple request, right? I checked in early at 11:00 am, and guess what? I got assigned room 1165 or something - very end of the hall, ground floor, closest room to the pool bar, and directly next to an entrance and exit!!!

I almost cried at check-in. Last time at WL, I got a ground floor room next to the loading dock. This time didn't sound like much better!
But fortunately I was prepared with a map of WL's rooms, so I knew right there that this room was a ground floor room near a major door, so I started politely begging for a better room - pleading that I was alone and didn't want a ground floor room. The lady CM went in the back, and then returned with a different room - a 3rd floor balcony room overlooking the inner courtyard and the spring, and near the lobby. And it was ready, even! I happily took that, and it was a GREAT room (even got towel animals every day!), and loved my 7 nights there.
But I just couldn't believe that a simple request of a non ground-floor room could be ignored - it leads me to believe that requests are ignored in general, and the computer just spits out a random room. I pretty much have had it with requests after that experience. What's the point? They make no difference. Seems better to beg at check-in. Oh well!
EDITED TO ADD: I believe I get these ground-floor rooms at WL because I am solo, and my theory is that they assign solos the unusued & left-over king bed handicapped rooms - basically whatever is left that isn't used by a family truly needing a handicapped-assessible room. I bet anything that my original room 1165 was king/handicapped-assessible.