No, it's because only Souji has the Courage to withstand any of the girls' chocolates.
I imagine Rise used cinnamon... a lot of cinnamon. Like, there weren't pieces of chocolate with cinnamon dusting. I imagine she just crumbled some Hershey's bars onto sticks of cinnamon.
How in the hell did Yosuke get both Chie and Yukiko? Unless they were plotting a revenge scheme against him.
Souji eats anything that's even remotely edible, like moldy miso, grass and some stuff that could no longer be identified. His digestive track is the strongest, it can handle anything at this point.