Correct. You have to steam roll or crack the corn kernel to get at the protein inside for digestion.
I believe that was one of the problems in the Irish potato famine. By the time the government in London realised the calamity that had struck Ireland with the failure of the potato harvest it was too late to buy up staple foods around Europe, the harvests in general were poor and by late Autumn everything had been sold.
Buyers in the US told them there was plenty of what the British called maize, what Americans call corn and what became known as Indian corn. Thinking this would do the British bought up shiploads of the stuff to sell to starving Irish peasants.
However the corn needed to be milled twice in special mills, none of which were available and the Irish, knowing no different, simply boiled it and ate it like that, apparently it caused excruciating pain as the kernels simply ripped through the digestive tract.
Thus the expression, “sh*tting niblets”