My company uses an even simpler system. Each team of 15 people gets assigned 15 desks.
Of course, neither of us nor the company really has hard knowledge of what is "more efficient", because despite being entirely driven by profit metrics and A/B testing there is still no real way to measure productivity for knowledge workers. And even if there was, employee misery wouldn't be part of the metric unless it measurably affected retention.
Thinking about it, why stop there? Negative desking is the future. A team of 15 could have -15 desks (or less, if they are high performers). Super efficient.