OK, I feel the need to clarify several things.
The 8:1 ratio is purely letting people know that 80 proof vodka contains 8 times more organic matter than does the normal distilled vinegar available in the US.
80 proof vodka is 40% organic. Vinegar at 5% acidity (the US standard) is 5% organic matter. Hence 40:5 = 8:1.
Now, that said, it should only be used as a very rough guideline when swapping from one to the other. The ability of any organism to consume them and the energy they get from them will depend on many factors. It is just a rough guide. It is not intended to be any more than that. Definitely not a recommended ratio when using both together, but rather a swapping ratio.
I personally know of no convincing reason to think using more than one type of organic carbon at a time is better than using only one type.
On the acid part, I also want to clarify. Yes, vinegar will have an initial pH lowering effect, and then as it is metabolized to CO2, there is even more pH lowering.
Vodka (or sugar or any organic) may seem like it has a smaller pH effect, but it does not. It simply waits for all of its effect to come after conversion to CO2, but overall it has an equally large pH lowering effect.
The net equation for vinegar (acetic acid) consumption is:
CH3CO2H + 2O2 ---> 2CO2 + 2 H2O
The net equation for vodka (ethanol) is:
CH3Ch2OH + 5/2 O2 ---> 2CO2 + 2H2O
So the net effect in each case is (and ONLY IS) the addition of two molecules of CO2 for each molecule of organic consumed.
The effect of the initial acid from vinegar is lost in the process (or, more correctly, is gained back later in the process).
CH3CO2H ---> CH3CO2- + H+ (there's that H+ which initially lowers pH)
BUT...
if you look at the metabolism of the acetate (CH3CO2-), it produces OH-:
CH3CO2- + 2O2 ---> 2CO2 + H2O + OH-
an that OH- exactly offsets the initially added H+.
So there is no more long term impact of pH using vinegar than in using vodka.
In all such cases, the pH effect may be wholly or partially offset with more aeration or using limewater.