Tarmack
Rhetorical Porcupine
I just place my play marker at the point I want to cut, use the slice tool and then copy my footage. Works okay for me, although the steps listed above will be a tiny bit faster, but haven't tried out that method yet.
He's referring to doing a copy of multiple overlaid elements all at the same time. Yes, you could cut each individual part at the same position in the sequence, but that's inefficient. It's not an issue if your video is only 2 or 3 overlaid bits at a time, but some projects can easily get into 10-15 different pieces (titles, video, images, audio, etc.).