Actually, I think I wrote too soon — I just tested Finder.app for moving (not copying) about 30GB of photos, around 400 or so selected RAW Files from one folder on a drive to another folder and the results were pretty quick.
Those same photos selected within Photo Mechanic, and dragged out of Photo Mechanic into a Finder window of another Folder (on the same internal hard drive) produced visual UI problems and took a very long time to move the photos, 10—20 seconds.
The red "Sticker" icon that updates with the amount of items selected fails to render entirely, Finder windows freeze up, and other little weird things happen before eventually completing.
These issues do no happen when moving content within Finder, only when moving from out of Photo Mechanic into a Finder window.