Looking at this, the dose of PA was the same in all the studies (750mg/day), and the timing was pretty consistent with other studies when they specified the timing, so that's not an issue. The inclusion of hydrolyzed collagen protein taken post-workout is also similar to other studies, so that's not really an issue either, and does well to replicate the other studies. The 3 sessions per week is also similar to the other studies, which used 3-4 sessions per week, but it seems that the total volume per week is a good bit less than the other two studies that actually specified this information (I couldn't find the information for Study 3).
Where Study 1 involved doing chest exercises 2x per week, with a total volume of 14 sets per week, Study 2 also hit chest 2x per week. I couldn't find the number of sets, but it involved 3 exercises on one day, and 2 on the other. Compare that with the NEW study that only hit chest 1x per week, with a total of 8 sets per week, from a total of two exercises.
For legs, it seems that Study 1, 2, and NEW all hit legs 2x per week, but Study 1 had 26 total sets per week compared to only 16 in NEW, and Study 2 had 4 exercises one day and 2 the other, while NEW only had 2 exercises on both days.
It seems that this new study has less volume (and less frequency at times) than the other studies. Maybe that's a contributing factor? I'll go through and check the gains made in each study to see if the studies with more volume noted greater increases than the new study with lower volume.