Assuming a uniform thickness and density, is the acceleration of a light sail not independent of area? I get the impression that the radius given is an upper li

Assuming a uniform thickness and density, is the acceleration of a light sail not independent of area? I get the impression that the radius given is an upper limit based on the apparent magnitude and assuming a high albedo. The light curve indicates that the object is tumbling, so a thin sheet would rarely (if ever) be oriented approximately optimally to act as a sail. I have not figured out how the authors have taken this into account in their calculation - could it be as simple as halving the area to give an effective value?