As shown in the Apstra 5.0.0 release notes, we introduced the following enhancement. 

[RFE-2685] Network Operating System (NOS) upgrade improvement (new in Apstra 5.0.0): 

To provide you with a smoother and more reliable experience, all interfaces are automatically shut down during the upgrade process to prevent potential issues, such as traffic blackholing. For example, this improves the upgrade experience when static LAGs are in use.

When you upgrade a Junos device via Apstra, you will see "interfaces disable" config in the pristine. 

As shown in the Apstra 5.0.0 release notes, we introduced the following enhancement. 

[RFE-2685] Network Operating System (NOS) upgrade improvement (new in Apstra 5.0.0): 

To provide you with a smoother and more reliable experience, all interfaces are automatically shut down during the upgrade process to prevent potential issues, such as traffic blackholing. For example, this improves the upgrade experience when static LAGs are in use.

When you upgrade a Junos device via Apstra, you will see "interfaces disable" config in the pristine. 

interfaces {

  et-0/0/0 {

    disable;

  }

  et-0/0/0:0 {

    disable;

  }

  xe-0/0/0:0 {

    disable;

  }

  et-0/0/0:1 {

    disable;

  }

  xe-0/0/0:1 {

    disable;

  }

..snip..

Apstra will render the interfaces config properly when you add generic systems to them. 

If you want to keep the interfaces up (not disabled), you can use the 'Skip Shutting Down Interfaces During Upgrade' option in the advanced settings. Please see the following document for details. 

https://www.juniper.net/documentation/us/en/software/apstra6.1/apstra-user-guide/topics/topic-map/device-nos-upgrade.html#task_yty_ppc_hdc