I don't know if I have seen the video you mention, but doesn't matter. It sounds as if the individual is doing the "silent cycle" as some refer to the process, and it is without question the easiest and safest way to start a new tank. You need live plants, some should be fast growing species (as so often mentioned, substantial floating plant species are the best for this). If the plants are obviously growing (and not declining), and depending upon which species and how many, you can add all the fish and everything is hunky dory. However, with someone who is new to this, I would recommend caution in adding fish. Just to be safe--it is one thing for me to have been doing this for years and years, because if something should go awry, I can readily see it starting and know how to deal with it. But when I changed over my substrates to sand some 8 or 9 years ago, I did each tank the same...the fish went into a running temporary (smaller) tank with the plants and some of the decor for shelter, the rinsed play sand went in, plants were planted and hardscape set out, tank was filled with tap water and dechlorinated, and all the fish were back either that day (with smaller tanks that didn't take so much time to set up) or the following morning (my 70g, 90g and 115g tanks took most of the day to aquascape, as I wanted to ensure it was "OK" before returning the fish).
I may do a water change after a day, or two, or three, but only if the tank is more hazy due to dirt from the sand (I do not rinse it endlessly, waste of time and water). And in my case, I know the plants are growing because they all come from the original tank or other tanks. But that is the crux of this method...fast-growing plants that are obviously growing. It is simply impossible to add too many fish if this is happening.
EDIT. Essjay's post appeared as I was typing.