This study seems to be pretty poor. First, look at the two charts. Compare the area where Whey protein is greater than the blend to the area where whey protein is less effective than the blend. I wouldn't be as concerned with the levels of phenylalanine as much as I would total BCAA. Also, the charts show that peak concentration of whey in the blood is about 40 minutes in. The FSR % was measured at 2 hours... This is when the blend is at its peak. If the FSR% was measured at 40 minutes, the chart would be wildly skewed toward whey having an advantage. This means that whey played a much larger role in muscle repair and hyptertrophy early on.
Look up research by John Ivy, the ideal scenario would be to take whey protein every 90-120 minutes for a few hours post workout.