I don't believe Scanning can be ruled out - that doesn't make sense to me. Unless Rodinal IS the Magic Bullet for Maximum Grain!
Stradibarrius shows MORE grain in full frame 35mm than I get with half-frame 35mm which I developed in Dektol to deliberately maximize grain.
Here is my benchmark for MAXIMUM grain, printed optically.
From post 27 of the thread Want more Grain...!
Original is a dirty border print on 11x14 with about 1 inch borders. Negative is 35mm half-frame, 400TX exp. 12/2014 batch 1781. (Exposed at EI 200 in an auto-everything Samurai - I scratched and taped the DX code to say 200).
Developed in Dektol 1:9 68-degrees F for 5 minutes.
This crop is about 2 1/2 inches by 4 1/2 inches (Roughly 1/4 inch by 1/2 inch measured on actual negative). In this image, JPG artifacts are smaller than the grain, this is a reasonable approximation of the actual print.