QE is measured at a spread of wavelengths, hence the plots. Peak QE will be quoted at the wavelength where this is highest. For Sony sensors to demonstrate QE in the 80s % isn't unreasonable given advances in sensor tech in the last 10 years. I'm not defending ZWO's data one way or another.
This (reputable?) doc makes for an interesting sensor QE comparison:
https://www.flir.com/globalassets/ii...sor-Review.pdf (note: they specify 530nm)
QE is a measurement of the output of electrons from photon strikes...mono or OSC makes no difference. The pixel in a mono sensor can't tell the difference between a colour filter in a wheel and a colour (Bayer) filter printed on. If a given filter is less efficient than another, that's a disadvantage for sure. Given the competitive market of the sensor business, it wouldn't make any sense for Sony to scrimp on the quality of the Bayer filter.
Of course, the mono is more versatile...and we can get "full" resolution for a given colour filter rather than the reduced colour resolution of OSC, which I think is what you're getting at?
These sensors have made me consider going back to OSC, the 2600 sure does look good on paper.