I wouldn't be surprised but have heard so many saying they do it I thought there might be something to it.
That might be older information....I don't think many people fax anymore, since the word got out that the resorts had started throwing them away a couple of years back.
Disney's process for handling requests has always been the same as other hotels. The guest asks for a certain location, view, etc at the time of reservation or calls back later, the request gets typed into the reservation record, the person assigning the rooms sees the request and picks a room that meets the request, if one is available.
The fax thing was a creation of Disney fan sites....because the front desk CMs sometimes mentioned that the resort had received their fax, people leaped to the conclusion that they were getting special treatment, and wouldn't have gotten their request without the fax. They post it on a board someplace, and before you know it, people are faxing poems to the room assigners, decorating their faxes with characters, sending long involved stories about how little Susie has ALWAYS dreamed of seeing the castle from her hotel room.....sending hundreds of faxes a day. The resort staff is inundated. The faxes go in the trash.
I never got why people thought it would make a difference, anyway. If the view or location you wanted was available, you would have gotten it without sending a fax, if the request was on your reservation. If it's not available, fax or not, you're not getting it.