I believe that study was done in Japan last year? The NIH calls is a 'small' regression, but come on, 12.9% in just 6 months is massive. We could, according to that study, remove a quarter of our plaque in just one year. I don't call that small, I could be plaque free in around 4 years.
Again we see no mention of which processes are taking place, the chemical reactions or anything. It simply mentions high HDL being responsible.