This was a key feature of the bet. It's within the first 100 gravitational wave detections. They're betting against an unknown distribution.
Neither side was saying that they wouldn't be found.
Neither side was saying that they wouldn't be found.
I presume that different masses of black holes result in different frequency waves, and that LIGO is not uniformly sensitive to all frequencies. Depending on the actual numbers, this would make these intermediate sized mergers either over or under represented in our data.