Well they themselves mention up to 100x enhancement in original bio luminescence. When you start with something absolutely invisible to naked eye in pitch black even after some time, 100x ain't that much.
> something absolutely invisible to naked eye in pitch black even after some time
Is it invisible, though? If it were, how would we even find out it's bioluminescent? And then, IIRC visual receptors in our eyes are sensitive to single-photon events. It takes a bit more for us to consciously perceive light, but not that much more[0].
Also, 100x enhancement is 20dB increase, which isn't little.
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[0] - https://math.ucr.edu/home/baez/physics/Quantum/see_a_photon....