I have heard the MTS stuff as well, and some of the theories re: deep roots etc.
Your neighbor i have no doubts about, so much of the information place out for general consumption is only partial, or place in it's entirety, but the person(s) Reading only use part of it, a great case in point came up last week re: a AC need/dont need convo. a user posted that old carbon releases back what it absorbed, That was the second time i had heard that statement ( just so happens it was n the same forum go figure). So i called the poster on it, they pointed me to an article about AC and they had seized on a single line: about adsorbed compounds being release back into the water column, what the neglected to read is that it is minimal and is generally the bacteria that is beneficial anyways.
Lighting also poses another one, many are so bad infected with the HLD that common sense simply quits functioning. More is better, Fert dosing regimes water change regimes etc etc etc, they take them as separate entities and not the entire BioSystem as intended.
So yeah i can see how your friend gets by with what others refer to as low light, i have had my lighting referred to as low low light, but my plants grow very well, i do not inject Co2 ( i do add Excel about 1 capful per day), i add trace ferts twice a week, and while my tank does nt require trimming once a week, i do need to trim once a month, growth is lush, and colors excellent. All that from a long discussion with a fella in UK, who is doing the same on .9 WPG, and still turning out a new Scape once a quarter, Impressive in anyones book i think.
Hoppy has also done some nice stuff on this site ie confirmed that indeed depth does affect light intensity, Posting a graph that shoots down the Bulbs are no good after 6 months etc etc.
What i would like to now find is a nice tabulated set of data points that indicated at what PAR level plants truly need, with that info, and all the other stuff out there, HLD can finally be but to rest or confirmed.