[l33tman]

The quantization of energy is mostly a 1920's observation that created the name Quantum Mechanics, due to a lot of interference effects among wave functions in various spherical or cylindrical symmetric arrangements that result in a lot of macroscopical effects seemingly being quantized, especially compared to the classical physics that preceded QM. But most are not fundamental effects, they are emergent.

When you go into smaller length and timescales, these quantization effects kind of lose or change their meaning.

So an electron doesn't instantaneously change between "shells" in an atom upon reception of a photon if you look closely enough, there are indeed smooth intermediary states and maybe the researchers are saying they detected subtleties in these states (I didn't read the original research article yet).