That’s an assumption, jumping to a conclusion. It is true for some people, since some people say it out loud, but it is not true for everybody, and calling it “unambiguous” is an unsupportable claim.

To the degree some non-voters say they don’t care, that’s still deeply complicated, enough that even taking someone’s word for it is a bad idea. Non-voters in the U.S. are not uniformly distributed, and thus there is evidence suggesting that not caring is already a function of class, race, education, gender, and age, among other things.

If you actually care about voting and about the truth, it does yourself a disservice to jump to a assumed conclusion that all non-voters are saying something unambiguous, that they’re all saying the same thing, that they all have informed choice, that they understand all the tradeoffs and implications, and that they really are fine with any outcome regardless of what they say.