Have they though
Lots of anecdotal reports, but haven’t seen anything approaching a scientific study - of which there are many linking algae with high nutrients - most of these are in natural water systems where algae is actually killing fish and other indigenous life forms (hence the interest and funding)
What many aquarists including Tom Barr have done, is added excess nutrients to an already thriving planted tank system ... which is hardly the same as what Green Aqua are referring in that Q/A session - the question was in regards of setting up a new planted tank as a beginning aquascaper and the benefits of planting heavily from the start, especially if you are doing a low light, non-CO2 system
George Farmer, Jurijs mit JS, Filipe Oliveira have all stated many times in their videos: plant heavily from the start to help prevent/limit algae - and change water
My personal anecdotes are of the sort where lean water dosing or limited nutrients (my tap water is basically rain water with minimal KH,GH and extremely limited even in micronutrients) doesn’t cause algae - I tend to keep fish from areas of similarly very soft water and minimal macro/micro nutrients, so just can’t see why I would keep them in the presence of high nitrogen’s, phosphates etc
And if Tom Barr has wild caught Altums in his EI tanks, I’d love to see them ... cause mine started to sulk at anything above 5ppm nitrates
ADA System promotes the concept of lean water dosing and enriched nutrient substrate
Green Aqua chooses to follow this method of planted tank development/maintenance, and that is how they counsel their clients as it’s the system they know and practise..... so if you want someone to tell you that excess nutrients are the way forward, listen to the Tom Barr videos