Your question made me curious so I looked for the study (which was for Li-ion cell phone batteries BTW) but couldn't find anything that looked familiar. So I have to wonder if the study was retracted.

But I have a phone app that helps manage charging to only 80% ostensibly for improved battery health, which is some support for the claim at least. But I can't provide proof so draw your own conclusion.

"Google says 50%" is not quite correct. From that study: "The smallest capacity loss is attained by charging Li-ion to 75 percent and discharging to 65 percent." which isn't really very practical. As I recall the 80% nbr was recommended as the best trade off between longevity and practicality.