We have booked a trip for May 6, 2017 to May 13, 2017 and the crowd calendar is showing resort crowd levels in the 5 to 6 range. However, when we try to book a value resort for our stay there are no rooms available. Won't the parks be busier then the crowd calendar numbers suggest when you consider the lack of available value resort rooms? We have traveled during this time period for the last 10 years and have never had a problem getting a value resort room.
Because of aggressive marketing, the WDW resorts are usually at or near capacity year-round, regardless of park crowds. It is the number of off-site people coming to the parks that is the principle driver of the different crowd levels throughout the year.
Also, the "Resort Crowd Level" numbers refer to the crowds across all of the parks in general, not how crowded the resorts that you stay at are.
Try booking the value resort for a few days of your trip. It is possible that you can get one for the first few days and move to another or a moderate for the rest of the trip.
Disney's website seems confusing and ever-changing to me. I just looked and first found only All-Star Music had rooms but as part of a package. Then I looked again and the Pop Century has ones as room-only. Others now showed as having rooms either as room-only or part of a package. Good luck finding something that works for you!
People make and cancel reservations all the time; the resort may have been full last time you checked, but cancellations could have come in. All it takes is one night to be unavailable for the no rooms available for the range you put in. I always call when booking a resort; I never book rooms on-line.
The cheer Worlds and Summit are during that time. Varsity has bought out the value resorts for the cheerleaders until Monday the 8th. We will be there May 4-9.