Protein powder doesn’t help directly with PE, but it sure does indirectly due to it contents.
Powder is typically taken with water/milk/juice, so being hydrated is healthy and increases your loads (not PE strictly speaking but still).
Powder contains amino-acids, with the most important one for PE being Arginine (NO precursor). More NO means more blood vessel dilation/blood flow so increased hardness
and supposedly helps with girth work for maximum expansion.
From personal experience I can only attest to the increased loads’ size.