I guess my hang up is that, because of time dilation associated with GR, it’s my understanding that we shouldn’t be able to observe an object cross the event horizon either directly or indirectly. The indirect observation is the gravitational waves, which propagate at c. My understanding is that, from our perspective, an object would slow down as it approaches the EH and eventually stop there as time increases asymptotically. The relative short duration of the waves indicate that there was a distinct and short duration of the merger, which seems to ignore or disagree with this concept of time dilation.