For the same reasons that peanuts are not primal. Because it matters if we evolved eating it or not.
Different species of tubers have different toxins to prevent decay/bacteria/fungus/insects and if we were not exposed to those toxins, we didn't evolve to handle them.
That's pretty much the whole premise of the paleo diet and how PB works. We are able to eat what Grok evolved eating and anything outside of that is inherently risky or downright harmful.
If we evolved eating a mint tuber then we are not automatically able to eat potatoes.
Potatoes contain the glycoalkaloids solanine and chaconine. Solanine is found in the plants of the nightshade family and not the mint family. The concentration of these glycoalkaloids in wild potatoes makes them toxic to humans.
The "Seven Deadly Sins"
Grains (wheat/rice/oats etc) . . . . . Dairy (milk/yogurt/butter/cheese etc) . . . . . Nightshades (peppers/tomato/eggplant etc)
Tubers (potato/arrowroot etc) . . . Modernly palatable (cashews/olives etc) . . . Refined foods (salt/sugars etc )
Legumes (soy/beans/peas etc)