Yeah, those three seconds were probably just to the kernel cache - on the contrary - most linux desktops has the unfortunate design decision that they showed the source to kernel cache progress instead of source to dest. I hope you tried to safely eject the drive before removing it and waiting the rest of the hour for that.
It might have been fixed in most modern DE’s right now - I’m not sure about the current state. But it used to be the problem…don’t ask how I know…