Mac reboots automatically after OS updates:

In MacOS High Sierra(10.13 all versions), Combo updates and Incremental/Supplemental updates for Mac comes with inevitable reboots to complete the installation. This is an inherent nature of these patches and that can not be modified using our Automated Patch Deployment definitions.

As of now, you can't skip/postpone reboots. It is advisable to schedule the Mac updates to non-production hours. If you have created an APD task to deploy Mac updates, configure deployment window to non-production hours to avert this condition. Or you can also have them installed at start-up. It is advisable to not have it deployed among the usual group of production machines, maybe a separate group and APD definition will do. We are also working on a prompt alert for the same to inform you when you are deploying these patches.

Cheers!