Hum, I'm not familiar with ruminant (i.e. cow) digestion but I think you're right in suggesting there's greater complexity here when associating cattle with the use of modern agriculture practices (haber-bosch process).
To direct the conversation towards solutions, Project drawdown (https://www.drawdown.org) mentions Silvopasture practices (closely related to Joel Salatin style farming). That said, reducing the amount of intensively-cultivated corn grown ultimately still means reducing the number of cattle (we're ~80-90% more than 100yrs ago) and seemingly less meat consumption per capita.
Regarding the parent's comment, the 1800 pounds-of-water-for-pound-of-beef figure seems to be sourced from https://waterfootprint.org/media/downloads/Report-48-WaterFo... (which won't say 1799 because it's metric) https://www.watercalculator.org/footprints/beef-king-big-wat... seems to aggregate various estimates.
To direct the conversation towards solutions, Project drawdown (https://www.drawdown.org) mentions Silvopasture practices (closely related to Joel Salatin style farming). That said, reducing the amount of intensively-cultivated corn grown ultimately still means reducing the number of cattle (we're ~80-90% more than 100yrs ago) and seemingly less meat consumption per capita.