We did not call ahead and did not get the loop we asked for when we arrived. In fact, we were placed much further away than we wanted. We asked for 1300 and got 1800. We were told everything was full, expecially since 2 loops were closed and were placed on a move list for the next few days. This didn't work with us as we have a hybrid with 3 fold out beds, and simply it would be a royal pain to pack up again and move, especially since at the beginning of the holiday we want to be at the parks, not at FW wasting 1/2 a day with take down and set up. My dh went into guest services and was told by the CM there was nothing she could do, the sites were all assigned. But dh knew enough about the system and thought that not everyone probably knows about requesting loops. So, he asked them to go through the closest loops to 1300 and check if all the assigned checkins for that day had actually requested those loops, and there were several who had not. We were able to "trade" sites, and in the end got the 1000 loop which we were fine with, even though the comfort station was closed.
So, at FW if you do not get your requested loop, they put you wherever and do not try to get you close to your request. So, when you arrive and don't get what you want, make sure you ask if all the assigned arrivals are meeting requests or not, and you may be able to get what you want, or a little better than your assigned loop... Since this was the first time we didn't get what we wanted, we will now always call ahead to save this hassle at checkin.