One of the greatest inorganic chemists is Karl Wieghardt. I wish one day I work for him. I try to read and understand his publications as much as possible and this one has just come out.
I am also providing a link to an interview with him here.
As I told before, I do not know anything about DFT, but I read (or sometimes skip) that part anyway. Sooner or later, I will (I hope) learn what DFT is and how to do those calculations.
It's the first time I have ever read the term "broken symmetry" approach (BS) and I didn't really understand what it is. But, it is OK. I am not worried about it yet.
As far as I understand, one of the most important results of the research is that the electron density caused by the reduction is localized on the ligands. You can see this on the spin density plots. I really liked the paper. Seeing the useful tables that show the formula of each complex, relevant reference, ground states, reduction potentials etc. really makes it easier to follow the paper.