Not so. Turnover rate is something you can measure. They can either choose to lie about it or not. Biggest weakness is subjective.
Honestly, the most surefire litmus test I've found is ex-employees who still speak positively about the employer.
Conversely, a very vague non-answer, like "I couldn't really say" may hint at a non-disparagement clause in exchange for a severance package (with an NDA covering the existence of the agreement itself).