Citation needed.
Beef can live on range-lands that aren't good for much else and requires very low inputs. If we didn't have a taste for grain fed finished animals it would almost certainly be many times as efficient as pork.
There definitely is land that is only useful (agriculturally) for grazing. There will be a subset of this land for which the tradeoffs favor grazing (there may be some land we could technically graze but as a society prefer not to, eg, to conserve water resources or leave an area "wild"), and there's no reason to not produce beef just because it's inefficient in other contexts.
Pork also has a niche like that -- you can feed pigs food waste. Some food waste can simply be eliminated and you always have the option to just compost food waste, but there is a non-negligible amount of necessary food waste (slightly spoiled produce, table scraps, etc). If you could efficiently funnel all of this food waste into pork production, you could reclaim those calories.