Great question; thought it would be appropriate to get a response to this question from the person who designed the light solution in the Grobo One
the low-down is that there's a lot to it so I'll try and keep this as short and sweet as possible. Typically, in the world of LED growing today you'll see a lot of companies producing or using blue/red spectrum LEDs, that cater towards the 440nm and 660nm wavelengths on the visible light spectrum. These wavelengths are necessary for two major plant functions: stem growth, as well as leaf growth, respectively. This is a bit of an oversimplification as obviously there's a lot more going on within plants that have different affects.
Just as an extreme example, the failure to keep certain light spectra in has significant plant morphology changes in plants that come from the same batch of seeds! Check out this video here for a great rundown of the differences that occur in the plants from CFL grow, to red/blue grow, to a red only grow, to a blue only grow: https://youtu.be/sfihE4IuFuU
You can see from the video that the red LED only lettuce grow had some elongated leaf growth, while the blue LED only had more of an upright structure.
Now, getting to the full spectrum part. Plants, since the dawn of their existence, have relied on the sun for growth. The sun, being what it is, has full spectrum coverage in the visible range, and even into the invisible range (Infrared and UV). I'll take a snippet from one of Grobo's blog posts on light to elaborate briefly on what each spectrum can achieve:
Ultraviolet — No exposure produces better growth
Violet — Enhances the color, taste, and aroma of plants
Blue — Increases the growth rate of plants
Green — Enhances chlorophyll production and used as a pigment for proper plant viewing
Yellow — Plants exhibit less growth compared to blue and red light
Red — When combined with blue light it yields more leaves and crops, depending on what you are growing
Far Red — Speeds up Phytochrome conversion which reduces the time a plant takes to go into a night time state. This allows the plant to produce a greater yield
So, the take away here is that while red and blue lights, possibly featuring a balanced white LED for better human visibility, can grow plants well, they may not be high quality in the sense of the overall potency, taste, colour, and texture of the plant. We don't want to just grow your plants automatically here at Grobo, we want to make them grow better for you.
I hope that answers your question