Scan source & dest at same time?

Hi, just wondering if it's possible to scan a source and destination at the same time. I have a NAS and external drive where there are many smaller files, and source scans take about an hour, destination scans (on the external) take even longer.

Running an unattended sync isn't the issue; it would be great if SB could cut down on total scan time by scanning the source and destination simultaneously.