I'm guessing this has more to do with the other models made at this plant. But, there will be a production hiatus for the last six weeks of the year.
https://www.cnbc.com/2017/10/12/gm-plans-to-temporarily-shut-down-detroit-factory-report-says.html
https://www.cnbc.com/2017/10/12/gm-plans-to-temporarily-shut-down-detroit-factory-report-says.html