Can you give a quick summary of why grass fed is not necessary. I can imagine a spectrum from grass fed pasture all the way to specialized diets with hay and grain, but this feels like an in-between to all corn fed beef.

There are a handful of factors involved, so I will just share the conclusion, which also admits that "more research is needed":

"We looked for _any_ way to spin the nutrition argument in favor of grass-fed meat, but the actual data are fairly easy to verify. If we whitewashed this for a more palatable narrative, the obvious flaw in that position might cast doubt on everything else we are suggesting.

We realize that this is a remarkably unpopular position. But, [...], an ethical clinician would never tell a patient that they should eat only organic vegetables or no vegetables at all. We have the same position on meat. For those who simply don’t have access to grass-fed beef, we still feel red meat in general is an important, nutrient-dense food for humans."