See the water flowing onto the plant bench (1 minute mark in the video)? See the plant pots sitting in water? This is an environmentally sound form of greenhouse sub-irrigation called ebb and flow. Since the water is recycled, there is no water run-off. Sub-irrigation is used in greenhouse growing all over the world.
If sub-irrigation is a professional method of watering potted plants, why isn't the USDA teaching it to consumers through the land-grant university Extension Program? All we hear is the steady drone of the drain hole mantra and nothing about modern methods like sub-irrigation.
Antiquated drain-hole based top watering wastes water, time and ultimately the plants. It is clearly an environmentally unsound practice propagandized by the USDA, a taxpayer supported institution.
Why is there no uproar about this? Why do houseplant hobbyists and gardeners seem to behave like sheep?