Yes, it is really a celebration of women!
I do not think that something would be not considered a celebration of women simply because it only included one body type. There are many types of women, and I do not think that every single type of woman would necessarily need to be included in something in order for it to be considered a celebration of women.
It would be crazy if people started to think that every single type of woman needed to be included in order for something to be a celebration of women because then, every time people wanted to celebrate women, they would need to gather together a collection of every type of woman, and it would take a long time to do so, thus, slowing down the process of celebrating women.
Furthermore, what if people kept complaining and it kept being broken down into requiring more types, to the point that people were saying, “This is not really a celebration of women unless we have someone of (every race) x (every eye color) x (every hair color) x (every body type) x (every sexual orientation)!” Then, people would need to gather over 1,000 very specific women to be able to include each of these types before being able to celebrate women. That would be horrible, and I do not advise it!