If you had read the article you'd know that's not possible, as solar wind would have had a negligible effect - unless the object was in practice a light sail. OTOH that hypothesis also doesn't sound correct IMHO - why would it appear to be tumbling with a fixed period?

The article does not talk about the possibility of an ultralight frozen cloud. It only mentions one kind of "solar sail" structure.

The tumbling was a reasonable interpretation of light curve data. But the data was limited, and something else may have been happening.