Probably significant. In this population of very severe patients, mortality was "only" 25% in patients managed without proning. Compare with mortalities around ~50% reported early into the pandemic in comparable populations.

Obviously difficult to say which part comes from patients presenting later in their disease course, doctors, nurses and respiratory therapists being overwhelmed with sudden influx of cases, and so forth -- and which can be directly attributed to premature and unwarranted intubation.