Not necessarily true. A lot of reefers use vodka in their tanks to introduce an algae bloom to lower nitrates.
I was not aware of that however, the issue is concentration of the ethyl alcohol. That coming from a fermentation process may well be much stronger than from a commercial product - 80 proof, 40%x volume. The ethyl alcohol in the vodka dosing is absolutely controlled whereas the accidental dosing from DIY CO2 is absolutely uncontrolled. Taking the precautions would be mush wiser than hoping that the concentration is not toxic. Also, we are talking about a freshwater aquarium, not a marine aquarium.