No, what they are saying is people say "Oh, they put a DSB on Freds tank and guess what, it worked. That means it works for all tanks".
The bottom line was Every tank is different. There are so many variables that can cause one system to work well where as other will crash. To prove their statements, they had created a lab experiment with DSB's versus Plenums and posed the question "which is better?". However, instead of just creating a single DSB tank and single Plenum tank and doing the test over a week, they had a fine sand DSB, they had coarse sand DSB, they did a mixture, then they did 3 tanks of each type, then they did the same with plenums, all the different types, etc. They ended up having quite a number of tanks, all the same sizes, all in the same room, all water sourced from the same location, all using the same test kits, etc etc. They added exactly the same amount of ammonia (8ml daily I think?) to simulate bioload in each tank (amongst other things) at the same interval then measured the results of ammonia, nitrite, nitrate and phosphate, salinity, alkalinity, pH (and some others) via test kits DAILY for (from memory?) 18 months.
Then they graphed the data. You could see that the differences for each system varied only slightly in the majority of cases (although alot with nitrate - fine sand worked much better immediatly than coarse) but then after 28 days, all figures worked out identical and stayed that way for sometime.
He is performing the same test with corals in the tank next to see if they have a differing effect on the same tests.
As I said, interesting to see. I would personally summarise what I got out of it as:
"what works in your tank might not work in mine"