Is it actually lasing or is it just fluorescence filtered by the microstructure? Definition of lasing entails nonlinear processes, the article seems to only indicate monochromaticity which can be achieved via linear filtering alone?
Additionally, nonlinear processes don’t immediately imply lasing either. It could be anharmonicity causing high order harmonics, which many biological materials will exhibit in response to intense laser sources[0]. In order to actually qualify as lasing you need to have evidence of coherent amplification.
[0] https://en.wikipedia.org/wiki/Two-photon_excitation_microsco...
I agree, the question if something is a laser is actually quite complex and a lot of things that were claimed to be lasers turned out to only be amplified emission. Nature photonics made a checklist for this very reason (note I did not read the actual article so they might have ticked of that list) https://www.nature.com/articles/nphoton.2017.28