You cite statistics and odds... Not a mathematical fact like 2+2 = 4
The odds that 2 + 2 = 4 is exact and 100%
The odds that your vote could determine the outcome of an election is a fraction of 100% thus not always a FACT as a possibility exists that it can.
You are the person who can't seem to comprehend the Theory is about the ability to predict or come up with a fair means of choosing among a choice of more than one in a societal event (like an election)... It has nothing to do with showing that those choices are meaningless.
(The song - Wheels on the Bus go round round round... popped into my head when reading the circular posts that have been going on here )
Give it up Prof. If there is one thing that Jl and ML and Matt have proved is that there is no logic for them. The circular logical fallacy is the constant fallback. It is notable that a frequent tactic is to take a part of a truth and try to claim that all of the assertions are truth because one part is. When that fails blame the reader, then circle again.
Frankly, JL and co. have no logical argument and still try lamely to convince people that 2+6= 10,000,000.
He/she pretends to be so much smarter than you that you just can't understand the logic, when there isn't any. Just as you point out, the theory does not say, in any way, that one vote does not count. It is trying to measure on an individual level multiple choice theory. It fails to account for the aggregate problem.
If one person decides to not buy gasoline, that makes no difference and affirms the Arrow theory. However, if 5 million people stop buying gasoline, then the Arrow theory becomes useless because of the aggregate problem. IT is the same faulty logic that Jl uses.