There was issues with my reservation last time I checked in, so I got chatting with the online check-in CM while the manager worked on it. This CM (at POR) advised that the online check-in CM's main goal was to get people into rooms that would be ready when they arrived based on the housekeeping schedule. Meeting requests is secondary, if they are even acknowledged.
I only have done online check-in this one time and got the exact opposite of my request, so that is how this conversation started. She said since I was arriving at 11am and the mansion I wanted to be in wasn't going to be ready until closer to check-in time, I was assigned a room that would be ready at my arrival time. I asked if they could switch me to the room I wanted, which they did. So, if you are going to ask for your request anyway, it's better and faster to just do regular check-in.