There have been similarly confusing reports about elite swimmers doing 80% of their training at low intensity.

John Urbancek, who largely brought zone training into swimming, would use your pace for a 30 min time trial as your zone 1 pace. For elite male swimmers this was easily under 60 seconds per 100. And even for average college swimmers like myself 1:05-1:08 per 100.

So yeah, The university of Michigan swimmers would swim huge sets of 100s on a 1:10 interval going under a minute on everyone. Not exactly what comes to mind when one hears “low intensity.”