Yes, as per comment above.

CThorSpillingRowArray supports createRowStream() also, but a spilling variety which isn't wanted here. I did consider adding an option or a variety of createRowStream to CThorSpillingRowArray, to allow it to return a 'plain' row stream for the array, but decided against it.
So the transfer to CThorExpandingRowArray is transfer the rows from a spilling to a non-spilling variety, purely to then get a non-spilling stream from.