Reading the article, it is unclear if they are comparing similar workloads. The article seems more focus on similar goals. There are likely interesting differe

Reading the article, it is unclear if they are comparing similar workloads. The article seems more focus on similar goals. There are likely interesting differences based on density and base body functions that scale in non-linear ways. I expect however that all those would be minor gains compared to exertion rate, especially when it comes to oxygen consumption. If we use diving again as an example, a person just floating still will be using less than half the oxygen compared to a person swimming against a mild current. Heavy work can easily go past 4x or higher compared to the oxygen consumption of a person in rest, which is a major problem for rebreather divers who are limited by their equipment in term of scrubbing co2 (for every 1x of oxygen consumed, 0.9x of co2 is produced).