I have noticed the progress of Muscle growth with and without POIS. POIS definitely hinders Muscle growth by 50-60% for me at least. Or I else I could just be taking less protein. But when I am not in POIS state, I put on muscle faster and lose fat even with the same diet. This could be the sleep quality and nutrition absorption that gets affected by POIS along with of course Muscle inflammation/breakdown/soreness kinda thing.