The definitions of factory farming they use here are based on the number of individuals per location. There are other metrics you may object to for the rest of that 25% too

For instance

Despite the consumer demand, however, approximately 95% of the cattle in the United States continue to be finished, or fattened, on grain for the last 160 to 180 days of life (~25 to 30% of their life), on average

https://extension.psu.edu/grass-fed-beef-production

I should also note that without demand for US beef and dairy production and consumption decreasing that's not something that can change all that much because there just isn't enough land for it

We model a nationwide transition [in the US] from grain- to grass-finishing systems using demographics of present-day beef cattle. In order to produce the same quantity of beef as the present-day system, we find that a nationwide shift to exclusively grass-fed beef would require increasing the national cattle herd from 77 to 100 million cattle, an increase of 30%. We also find that the current pastureland grass resource can support only 27% of the current beef supply (27 million cattle), an amount 30% smaller than prior estimates

[…]

If beef consumption is not reduced and is instead satisfied by greater imports of grass-fed beef, a switch to purely grass-fed systems would likely result in higher environmental costs, including higher overall methane emissions. Thus, only reductions in beef consumption can guarantee reductions in the environmental impact of US food systems.

https://iopscience.iop.org/article/10.1088/1748-9326/aad401