Workbench Class not found error when upgrading from acquia_cms:1.5 to acquia_cms:v2

[iHassan]

I came across an error in acquia_cms_common_update_8004() function when I updated acquia_cms from v1.5 to v2.

drush updb showed below error and aborted the update,

error: class Drupal\workbench_email\Entity\Template not found

I learned that the workbench_email module has to be enabled first to continue with the update.
drush en workbench_email

Just wanted to know is this intentional or should this be considered a bug if workbench module is not enabled and we try to update the database?