Yep, that’s what it looks your screen shot in showing - very odd.
I’m running Duplicate as a service, not the tray icon as you seem to be using, and while I did see a spike while it ran (with a max of 940MB) it went back down to 57MB once the job was completed (note that the machine did fall asleep during that time, so it’s possible some cleanup happened when Windows woke up).
It’s possible there is different memory usage rules in the tray icon vs. the service…