They're omitting the fact, that a lot of the biomass we're eating comes from farming. Those plants that collect carbon dioxide from the atmosphere use a lot of synthetic fertilizers to grow, which itself uses A LOT of fossil energy to be produced.

The CO2 emissions per calorie of food varies almost 3 whole orders of magnitude between different food types:

https://ourworldindata.org/grapher/ghg-kcal-poore

At the same time, our CO2 exhalation is about the same per calorie of food, regardless of source. So it's more fair to describe our baseline biological needs and bodily functions separately from our economic consumption of the products we prefer to consume (food or otherwise).

So I still think the focus on the raw calorie count of our consumption (and the accompanying CO2 exhalation) obscures, rather than explains, how our food consumption contributes to climate change.