I am not trying to be argumentative, so please take this as intended advice.
None of us can possibly know how the fish think about the situation we force them into, nor can we assume they are fine. Those who are trained ichthyologists do know that these things do negatively affect fish. That is plain scientific fact. Detrimental effects do not mean the fish is necessarily going to die, or change externally in any way. But it is causing additional stress, and this can lead to other issues. Stress is the direct cause of 95% of all fish disease in an aquarium; the pathogens/protozoan have to be present, but it is the stress that prevents the fish from fighting them off.
From that generalization, we can turn to specific species. Neon tetra and green neon tetra are very closely related species, along with cardinal tetras. These will naturally shoal together in an aquarium. The glowlight tetra is a more distant cousin, but when faced with the lack of its own species it will not surprisingly tend to look for alternative species. Individual fish within a species can also react differently to stress. I have over my 30 years had various species of shoaling fish that have died off through old age, leaving one or two or three for a time at the end; most of them have clearly shown increased aggressive behaviours, especially when it is down to the last one. If I cannot acquire, or do not want to continue, with the species, it is best to leave the last ones where they are, in known surroundings, and hope nothing becomes too serious which would necessitate the removal/euthanization of the fish. But that can sometimes happen.
All of this is programmed into the fish's DNA, and no aquarist should think they can change the way a fish behaves, responds, or handles a given situation.