This is interesting, I will give you that.
But it's one study among many others that say otherwise.
I mean Philips has built an entire sideline business geared around the importance of LED spectrum as well as an entire series of lights based on the whole "light recipe" thing.
http://www.lighting.philips.com/main/products/horticulture/light-recipe
That's a lot of money to invest into an idea that doesn't show promise.
Somewhere I video from a British TV show where they toured one of the Philips test centers, it was very enlightening (no pun intended).
In the same TV series they show a bit about a guy who changes the spectrum of light on certain herbs right before packaging because this allows the herbs to deal with the standardized cold shipping conditions and still arrive at grocery stores fresh.
In the attachment is one study I found that shows that light spectrum does in fact have an effect.
Also in the attachment is the "Cornell Hydroponic Lettuce Handbook" it has lots of information about lighting, specifically LED lighting.
There is also another study, I have the pdf somewhere, when I find it I will post it.
It shows how plants (lettuce again) grown under specific spectrum can differ in both the way they look and the nutrients they contain.
This paper helped me when I was making the lights for my "greens" shelving units and I have some of the most perfect lettuce and bok choy that come out of that set up...
Here is a YouTube link to a video that does something similar.
It clearly shows how spectrum directly influences the plants...
Another way to easily test this on your own is to periodically do brix testing on your leaves, which can be done using a cheap refractometer or something like a SCiO pocket spectrometer, it will give you an idea of the nutrient content in your plants, not that you will be eating the leaves, but the leaves are necessary to make flowers...
Ultimately the point of the grow should be a quality yield, not the weight.
We have commercial growers who will soon be ruining the industry by focusing purely on weight while producing trash product and I am sure in the very near future they will even begin (if they haven't already) using recombinant DNA and CRISPR to produce GMO weed.
When that happens it will be the folks who still give a shit and have good, quality yield who will benefit the most (look how companies selling organic food are making bank right now).
Just my 2 cents...