Here is a nice example of a 100cm tank lit by two T5s approx 40cm above the water, light duration is 6 hours a day.
The tank belongs to Mark Evans and just made Rank 137 IAPLC entry.
We have lots of similar tanks on our forum using 2 x T5 or LED..
I've seen some of Mark Evans stuff, excellent scaper and photographer, but he really is a professional so hard to compare what he does to a typical planted hobbyist here. His knowledge and dedication far outweighs IMO difference in light, etc. That tank looks longer than 100cm it looks like a 120cm. Also most of Mark's stuff that I used to see had a MH component to it. Are you sure there wasn't any other light on that setup besides the two T5 during the grow out.