The original 2015 finding has not been overturned — the statistical signal it identified is still there, in multiple subsequent studies, with multiple analytical methods.

But neither has its explanation been definitively established.

The scientific community is in the state it is supposed to be in when working on a complex question with limited evidence: multiple plausible explanations on the table, progressive accumulation of evidence that constrains the possibilities, honest acknowledgment of what is and is not known.

This is what scientific progress actually looks like most of the time.

It does not look like a sudden revelation that immediately resolves a long-standing question.