About two paragraphs later.
"In this issue of Molecular Cell, Foit et al. (2009) have created a very interesting genetic selection-based approach to understand protein stability in the cell."
I think that you misunderstand science. It's a process. Scientists don't start off with an answer, they find it. Just because one paper says something ambiguously related to certain areas of evolution being complicated, or "mysterious", doesn't mean you can take it out of context.
These people did say that the selection of protein sequences are an area where knowledge is lacking, but they are also looking to explain the mechanics better.
No scientist would ever say we know 100% of everything on a certain subject, evolution being one of them.