Interesting. So if I am understanding you or the article properly, it is not so much that a plant specifically needs 660nm light, it is just that that wavelength gives the greatest photon->CO2 conversion rate.

Hypothetical: So if a monochromatic LED could convert 50% of its electrical energy to yellow light, it would outperform a monochromatic LED that could only convert 25% of its electrical energy to deep red light. Is this (more or less) correct?

Or does our fave plant require a SPECIFIC trigger at 660nm that cannot be compensated for by other spectra?