A document describing their findings was presented last year.
I'm currently reading The Secret Notebooks of Agatha Christie and really enjoying the look at her process. As a reader I always found her plotting, and especially her fairness with clues, to be downright intimidating (put me off trying to write a mystery for years, frankly!) Sure, you could quibble about some stuff, and there were times when the ingenious solution was not really plausible. The stories made internal sense and, as I say, the plots were solidly constructed.
But. I read Postern Of Fate, the final book she wrote, a few years ago and then told every mystery fan I knew to avoid it. I didn't do that because it was a bad book, even though it was. I did it because it was incoherent to the point that I was sure Christie was suffering from dementia when she wrote it, and I didn't want anyone else to experience the helpless sadness I felt without at least a warning.
Anyone can have an off-book, but Postern was bad in ways that suggested some sort of diagnosable mental illness, and given her age at the time the first thing I thought of was Alzheimer's. I really wish her publisher had elected not to issue that book. It was extremely painful to read.
So--these investigators make a good case, but even as a layperson who'd read Christie's earlier books I was pretty sure something was wrong.
Do, however, read the notebooks. Actually, read her books first and then the notebooks, because there's a lot of detail given about her plotting, and spoilers are more enjoyable when they aren't, if you know what I mean.