I believe that in reality " targetting photoreceptors more equally and not overloading some while underdriving others" , hardly ever happens.Yes, that's why we believe Far Red is so interesting, as it appears to drive both photosynthetic and a number of photomorphogenic responses that are complimentary. One issue is that Far Red is costly to provide in terms of LED efficiency as most 730nm LEDs we've looked at have been around 50-55% efficient, and depending on what spectrometer you use, it does not show up as PAR and therefore is not necessarily counted in umol/j numbers that encompass the traditional 400-700nm range. So it makes your lamp look less efficient compared to a more traditional LED grow light, which not everyone understands.
Certainly we believe having a "true" full spectrum is advantageous – that has always been the philosophy behind the High Light design. But efficiency is always going to come into play and not just due to "bragging rights" but because even though spectrum makes a difference to plant growth, providing more photons (up to a point) appears to make a bigger difference. Although I have often wondered if in fact having a more complete spectrum allows you to push the boundaries of maximum DLI by targetting photoreceptors more equally and not overloading some while underdriving others.
The spectra you describe above is really just a drive for greater efficiency, as the cheapest colours you can combine (in terms of LED efficiency and quantum yield) are 660nm mono and CRI70 white phosphors around 5000K. CRI80 3000K is usually thrown into the mix to balance out the orange-red end of the spectrum and does not hurt efficiency that much when mixed in moderate numbers, but I do have a little laugh to myself every time I read the words "Full Spectrum" when looking at an LED lamp that has almost no light under 440nm, almost no light over 700nm, and almost no light at 480nm. When you look at all the photosynthetic absorption peaks missed out by most LEDs, you do start to wonder. But it also shows just how adaptable plants are.
This would be due to photoreceptors being produced by the plant which target and maximise energy transfer and photosynthesis in relation to the incoming light. It definitely shows how adaptable plants are, as you said above
Is that a valid test, as lettuce is a low light user (I'm told). Maybe tobacco... but that may not be legal (in Australia).