Usage patterns
必ずしも〈事〉とは限らないit is not necessarily the case that ~
Expensive wine isn't necessarily delicious.
必ずしも〈事〉とは言えないone can't necessarily say that ~
You can't necessarily say his opinion is correct.
必ずしも〈形容詞〉くないnot always/necessarily ~ (adjective)
More isn't always better.