Correct. The vast majority of US cattle are grain fed/finished.
"If all the grain currently fed to livestock in the United States were consumed directly by people, the number of people who could be fed would be nearly 800 million," David Pimentel, professor of ecology in Cornell University's College of Agriculture and Life Sciences, reported at the July 24-26 meeting of the Canadian Society of Animal Science in Montreal. Or, if those grains were exported, it would boost the U.S. trade balance by $80 billion a year, Pimentel estimated.
With only grass-fed livestock, individual Americans would still get more than the recommended daily allowance (RDA) of meat and dairy protein, according to Pimentel's report, "Livestock Production: Energy Inputs and the Environment."
"If all the grain currently fed to livestock in the United States were consumed directly by people, the number of people who could be fed would be nearly 800 million," David Pimentel, professor of ecology in Cornell University's College of Agriculture and Life Sciences, reported at the July 24-26 meeting of the Canadian Society of Animal Science in Montreal. Or, if those grains were exported, it would boost the U.S. trade balance by $80 billion a year, Pimentel estimated.
With only grass-fed livestock, individual Americans would still get more than the recommended daily allowance (RDA) of meat and dairy protein, according to Pimentel's report, "Livestock Production: Energy Inputs and the Environment."
https://news.cornell.edu/stories/1997/08/us-could-feed-800-m...
To add to that, the argument that animal pastures cannot be used for anything else has been proven demonstrably false time and time again. They are not usable for modern day agricultural monoculture cropland, which is the metric that the studies use and I'm sure the commenter is referring to. That does not mean by any stretch of the imagination that they cannot be rewilded or even transformed into usable farm land again through long term soil regeneration methods such as permaculture farming or effective through growing climate appropriate polycultures.