Summary

Customers cannot import a Confluence Cloud Site backup if the Atlassian Cloud site for them has Jira. When trying to import, they get the following message:

If your Atlassian Cloud site has both Confluence and Jira, site import is not available. To import an entire Confluence site, you'll need to import the spaces one at a time. Learn more at Import and export data.

Suggestion

If customers are using Confluence and Jira, they cannot import Confluence Site backup from a backup created using Backup Manager on Confluence.
To restore a Confluence site, the customer has to export all spaces and then import those spaces one by one. This will take a lot of effort on the customer side.

If customers can create a backup of the Confluence Site and can export all spaces individually, there should be a feature to restore Confluence Site backup even if they are using Jira.