It’s true according KREX News in Grand Junction, CO. Another benefit is that horses not suited to life in the wild are eliminated. See this report dated 03/20/19.
Where did they get this information? From the nutjobs at Friends of the Mustangs (who helped the BLM set the traps last fall ahead of the Little Bookcliffs gather)?
Wild horse roundups increase the likelihood of inbreeding due to the reduced size of the herds and horses unfit for life in the wild die off.