Uh, no. That is not what the article says at all.

The text explicitly says that vegetarian diets are not part of the solution. Either now, or under the system he proposes.

He's very clear that eating a fully vegetarian diet now is worse, footprint-wise, that eating a mildly omnivorous one.

He's also very clear that while eating a vegetarian diet under his proposed system would be just about possible, it is built around the assumption that most people will be eating meat, and that it would form a primary food source for the months of year when plant-based sources were scarce.