Hi,
That is pure nonsense. The way Sony minimizes diffraction effects is by increased sharpening, hopefully just on JPEGs.
Please realise that diffraction is simply a property of light. Nothing sensor, lens or camera makers can do about.
But, having more pixels is useful in sharpening. Within some limits, the loss of sharpness due to diffraction can be compensated by sharpening, and that sharpening may work better with smaller pixels.
Best regards
Erik
PS. You can view the problem in the frequency domain. You essentially multiply the MTF of all parts of the processing pipeline. A higher resolution sensor will have a better MTF than a lower resolution sensor, so it will transfer more fine detail contrast.
Sony cook the RAW files to minimize diffraction effects (as they said during A7r's launch) that will dominate when non system lenses are used.
Does this (RAW cooking) extend to Canon EOS lenses adapted via a "smart" adapter?
TIA!