You wish to understand the file transfer behavior with internal agents and PDQ Deploy.
Target computers deemed to be 'Internal' will continue to use the same runner service and the deployment method as in all previous versions of PDQ Deploy. External agents cannot have files 'pushed' to them, they must always pull from upstream PDQ servers.
When your Deploy Central Server is configured to 'Push' and you target an 'External' agent, the agent will automatically pull the package from PDQ upstream providers. If this were not the case, all external agents would fail deployments until the preference was changed to pull.