Thanks Lars...
One additional thing we figured out was you can't select from a local table in the EXEC statement.
Per the docs which I missed:
One cannot use SQLScript variables in the SQL statement (but when constructing the SQL statement string).
So we copied the SQLScript variable results to a HANA table then used the HANA table in the EXEC insert to write it to the ABAP table.
One too many steps but it works and it's only being done once, not repeatedly.
Thanks again.