This is a very interesting interview. Thanks. But, the problem is not with quantum gravity. It is with a misunderstanding of what is quantized in quantum mechanics. It can be easily shown that the energy of a photon is not quantized.

First, the photons that were emitted early in the development of the universe started out as very high energy photons with very short wavelengths. We now call that the cosmic microwave background. And as the name states, these cosmic photons are now what we call microwaves with much longer wavelength and much smaller energy, but they are still the same photons that were emitted approximately 10.5 billion years ago. How can that be quantization in energy? So, what is quantized here? The formula for the energy of a photon is: E=hc/lamda

Why doesn’t the amplitude of the electric field strength enter this formula? It is because the electric field strength is the quantized entity and it is the same for all photons. Therefore we don’t need to take that into account. That amplitude is embedded in the constant h (Planck’s constant). Why is the amplitude (field strength) of a photon constant? Because that is a property of free space.