It's important to keep in mind the rebound effect and its impact on these sorts of things as the advertised "savings" often don't occur in reality as any such change (e.g. everyone giving up beef and eating beans) doesn't exist in a vacuum, but is rather accompanied by other behavioral changes that have impacts.
As the article you linked says: "That is, even if nothing about our energy infrastructure or transportation system changed—and even if people kept eating chicken and pork and eggs and cheese—this one dietary change could achieve somewhere between 46 and 74 percent of the reductions needed to meet the target."
The problem is that it's not the case that nothing else changes. This has been researched and when people follow these sorts of diets, the incremental financial savings are generally spent on something else that has associated energy use/carbon emissions/etc. So, in aggregate, the net impact of people switching to plant-based diets, while positive, generally is not nearly as favorable as some articles claim.
It's worth noting that in theory it could save that, so it's probably most accurate to think of it as sort of an upper bound of benefits. For example, for someone pursuing ERE who eliminates that cost and actually puts it to carbon-neutral spending, it's accurate enough. So it's definitely a worthy thing to do. But it's not the case that, in aggregate, people who switch to plant based eating are going to do that - some of the spending will go to trips, consumer products, and other spending that carries environmental costs, offsetting a material portion of the benefit. Articles like that one, unless I'm misunderstanding and they account for the rebound effect, are overstating the (net) benefits.
Again, not that I'm rationalizing animal-based diets. I'm >90% vegan myself, in large part for environmental reasons, but I think those sorts of articles overstate the case a bit.
See the following article for one such study/the idea. I've seen different numbers put out there, and the specifics aren't the important part, just understanding the idea of the rebound effect.
https://www.sciencedirect.com/science/a ... 0915002153