No, you do not need to subscribe to the Salesforce report in order for auto-import to work.

When you connect a Salesforce report to a Flow for auto-import, Groove will automatically check that report every three hours and will auto-import any new Contacts and Leads that appear in the report if they meet your Flow’s criteria (i.e., are not blocked from being imported by a Block Import Rule or the Flow Safety Setting).  If your team has real-time auto-import enabled in your instance, then Groove will check the report for new Contacts and Leads more frequently.  

Groove uses the Flow Owner’s permissions to check and run the Salesforce report.  As long as the Flow owner has access to the Salesforce report and has Salesforce permissions to run reports, the auto-import should run successfully.  Please be aware of the following scenarios that could impair auto-import for a Flow:

• Flow Owner Does Not Have Permissions to Run Reports in Salesforce: The Flow owner’s access level for reports in Salesforce must include permissions to run reports.  This guide outlines the different report access levels in Salesforce.  This guide covers how to adjust a user’s report access levels in Salesforce.  
• Salesforce Report Is Not Shared with Flow Owner: If a user with edit access to the Flow connects a Salesforce report that the Flow owner is unable to access for auto-import, Groove will be unable to run the report.  More information on sharing reports in Salesforce can be found here.  
• Flow Owner Becomes Deactivated: If the Flow owner becomes deactivated in Groove (e.g., they have left the company, moved to a role that no longer requires them to use Groove, etc.), Groove will no longer be able to use their permissions to run the Salesforce report.  In this case, we recommend that an admin transfers ownership of the Flow to another user using the Flow Transfer Tool so that their permissions can be used to run the report.  This new Flow Owner will need to have run access to the report in Salesforce.