Yeah. I mean-- usage sometimes differs. I don't want to make this exactly a definition debate. But look at how Vaniver used the word:

Alice saying "nothing is wrong" rather than "let's not talk about it now" is an out-and-out lie. It's not clear that Bob inferring that Alice is repeatedly lying would reflect better on Bob.

That usage suggests to me a meaning of liar that implies deceit (though Vaniver later said he didn't mean to imply that).

I do think it would be a social/linguistic error to respond to weirdness, joking hyperbole, or sarcasm with with "Liar!" or similar variant in a sincere tone.