It's not the method of making the request that makes the difference. It's the availability of the room you want.
Whether you call, fax, or use online check-in to make your request, all you're doing is putting information in the request field on your reservation record. If you call, the CM types it in while you're talking to them. If you fax, whoever receives the fax types it in. If you check a box during online check-in, the program writes it into the field.
The room assigner looks at that field when selecting your room. No matter how you've made the request, they do try to get what you want. Sometimes they just can't, because the people occupying the rooms that meet your criteria aren't checking out on your arrival day.
Looking at your post, if I'm reading it correctly, you usually request quiet pool view, which is a simple request, and easy to meet. There are lots of pool view rooms.
Your request for second floor, close to lobby, courtyard view, is actually three requests, and every request you add decreases the number of rooms that meet your criteria, making it harder to fill.
Using totally made-up numbers here, let's say there are 100 rooms on the second floor. Maybe 25 of those are considered close to the lobby. Maybe 5 of those 25 have a view of the courtyard. Now luck comes into play - are any of those 5 guests checking out on your arrival day?
Again, if I'm reading it right, the difference is just a matter of odds. You usually request something that a good number of rooms can meet. This last time, you'd narrowed it down to a smaller number of possible rooms.