I think it just depends when in May you are going.

For example, our wedding anniversary is May 15th. Originally, we were going to DW from May 13 - 17th to include our anniversary. However, I noticed that the only rooms available at the YC during that time were the expensive rooms like suites and concierge.

That was almost two months ago. My
travel agent even had problems coming up with standard view rooms at the resorts we were considering to stay at for those dates. Last week I ended up booking from May 18th to the 22nd, and everything was open, including standard rooms. The only resorts I noticed that were not offering rooms readily were the "home away from home" resorts.
I just looked again at the Disney site, and now the YC has everything open except lagoon view concierge. I checked GF, OKW, and POFQ and they all had availability for all level rooms.
When I booked our stay through my travel agent, she said she and the other agents were just discussing room availability. She said they were surprised to see all the availability for May 18 - 22nd because just a short time ago, she said nothing was available at the YC for those dates. She thought maybe they opened up blocks of rooms that were originally held over for some reason.

I don't know what this means to all of us May DISers, but I'm guessing the less availability for the dates you are travelling, the larger the crowds. JMO!