Saavik, as a young cadet in TWOK, doesn't yet know this. That's why she's so upset with Spock's "lie." His explanation, "I exaggerated," gives her something to think about, and look at from a different perspective.
That is one aspect of Saavik I really identified with, as a matter of fact. When I was a kid, I was extremely literal-minded (still am, somewhat, I'm an Aspie after all). I remember being told that lying is wrong, so I never did it, and I understood lying as "telling something else than the whole truth". I did not know that some truths were best left unspoken, if you will. Got me in trouble when my French teacher got it in her head to ask me if I enjoyed her class and after that if I liked her as a person... I was 9 years old and answered truthfully, after which she complained to my parents, who then tried to explain to me the idea behind diplomacy and polite non-answers!