I thought that 2019 article is now "answered" by the fact that we have multi-messenger observations of gravitational wave events that confirm fading light curves.
I believe we still only have one multi-messenger observation. One observation has infinite variance =P.
They're ALSO not independent observations, though. The LIGO observation was made, and then the directive was "go look for correlating events". That's a dependent observation.
To be truly independent, they would have to inject synthetic data (say 3x) into the observation reports and make sure that the multi-messenger results don't correlate with the synthetic data, much like GP says they did "at the beginning of LIGO" with internal (non-multimodal) signals.
This would have the side benefit of making the analysis pretty simple to do (just a chi-squared analysis) and you don't have to have a PhD in signals analysis with a specialization in the filters used by LIGO to believe with a high confidence that 1) GWs exist and 2) LIGO is actually measuring GWs.
