Carbohydrate replenishes the glycogen levels, yes this is nothing new. Protein does stimulate protein synthesis which builds new muscles, yes. These things are pretty basic stuff concerning training physiology.
But this is the first study i have come across that actually shows increased performance in cycling concerning the timing of protein+carbohydrates and to quote the researchers "This is the first study to report that CHO+PRO supplementation during the first 2 h of
recovery compared with CHO supplementation alone resulted in greater sprint performance
18 h later. "
One thing to have in mind is that the total intake of protein is higher in the group with the CHO+Protein compared to the CHO group only. This is something that i think could effect the results.