Why? Because just yesterday there was an article on the front page touting how Toyota was testing putting improved solar panels on the roofs of their vehicles, and that article quoted an efficiency of 34%, well above the "max theoretical limit" given in the present article: https://news.ycombinator.com/item?id=20364348.
So I guess my question is how would the proposed manufacturing process in this article be an improvement? Cheaper manufacturing costs? Even higher efficiency if you had "multi-junction cells" made using the processed discussed?