I’m not entirely sure why you have the behavior you describe: in my example, A1:E8 is filled, row 9 is empty before updating, and I add four string-columns with the Google Sheets Updater. This is my result:
Then again, I don’t know too much about google sheets - why are your cells marked in green for example? Could it be that they are somehow protected/treated specially? Which AP version are you on?