I do not agree at all. Well, kinda... it is not JUST lights, but they are by-far the most important thing. I have been doing this for just over 20 years. My tanks have survived alk swings, parameter swings, alk down in the 5.0s, temps down into the 60s with ice storms and even a kalk reactor dumping and PH in the 9s. The common denominator is that I feed them the best energy that they can get from Metal Halides and they are super hardy because of it - I do think that MH are superior to T5 still (heat is no issue for me), but I would use T5s in a heartbeat if I had to. If you have a 8+ bulb T5 setup with a good fixture or a good MH setup, then you are 75% of the way there and you can have pedestrian stability and water parameters and succeed well above average... if you can also have elite stability and parameters, then you can have an elite tank. Every LED lit tank that is near elite has to be dead-on-balls-accurate (it is an industry term) in every step along the way. All of the additions of T5s to LEDs and seeing everything get better and easier is a step in this direction also.
I am not saying that the best lights and a under gravel filter will get the job done, but with the best lights, you can just be pedestrian in a lot of other areas. The best water quality with pedestrian lights will not yield the same results... but changing lights can have the jump that he saw.
Just to be fair, I am picky and I have seen a lot of tanks over the years with my own eyes. I am the guy who walks into WWC and sees a tank that is 75-80% of what it could be. ...or walks into Vivid and thinks that their tank a decade ago was a lot better... a lot better. I understand that most folks will never have a tank like Vivid or WWC, but I do and I know the difference. I also am only into Acropora - I do not even allow any montis, birdsnest, poci or stylos in my tank. I am the ultimate doocher and acro snob... sorry about that in advance... I do realize that this makes me hard to like.