As per the SQL script only the columns SKU1 and SKU2 are being dropped. Since the previous data type for them was floating point number a prefix 'f' was added to the names provided by you. At DB level the column names were fCusSKU and fCusSKU2.
Now since you are converting them to string the prefix will change to s. So old columns will be dropped and new columns will be created.
As you said, you never used the columns SKU and SKU2 for storing data against a profile, it should be fine to let the product drop those old columns.