Oh it was poorly worded. Of course data frames represented as columns so it SoA on other hand in haskell it’s easier to work with AoS thus AoS→SoA.
But this problems goes deeper. Say we want to make typed data frames. One may want to specify that type of row is product data type A. Then we have problem of figuring out what are columns, how they should be represented and how to address columns. On other hand one will want to create ad-hoc data frame say with column x::X and y::Y. Now question is what is type of row? vinyl and other libraries for extensible record try to answer that question.