Peas, pigeon peas, soy beans, in fact any legume seed is toxic to chickens. The truth is that peas and beans give chickens gas and chickens are unable to poot.
Chickens only eat soy beans in pellets or mash form because the soy beans have first been ground, roasted or steamed at high...
The real reason is political. As smart or as dumb as a chicken is or can be I have never found a Democrat or a Republican chicken and I have kept quite a few chickens over the year. In this one political aspect maybe chickens are smarter than us humans.