I do it like he did, using the entire sheet. Easier to make it perfectly level and plumb and I go back and piece in where needed. I also pull out pieces where receptacles go, cut them independently and replace them in the mix.
It's interesting you mention the latter, because I used to cut out the receptables like perfect rectangles. Now I find it easier to pull out all the mosaic pieces necessary to fit the sheet over the receptacle, and add in the cut pieces after. Rectangles in the field are difficult cuts.
However I'm still not seeing the benefit of doing that on the edges. Why do you find it's easier to make level? It seems a straight cut on the tile saw does the job.