One of the most significant findings are the larger black holes which have been observed merging. The largest one appears to be 90 solar masses. The high brows in BH formation might have some problems with how these formed, especially as they get bigger with more observations. If they start seeing them in the hundreds of solar masses, it will get very interesting. There is no apparent mechanism of core collapse supernova to produce such large BHs from giant stars.
While they don't indicate distance on these observations, it seems likely the largest merging BHs are from the more distant past. And the larger they get, the more likely primordial black holes are involved. Once again, time will likely tell.