 News of an alternative sense is like news of an alternative spelling; there is no evidential impact (except for meta-linguistic beliefs about the nature of words). Your assertion that ‘All bachelors are men’ is robust with respect to the news that ‘bachelor’ has an alternative sense in which it means a male seal. Assertions are not robust with respect to news of hidden generality. If a South African girl says ‘No elephant can be domesticated’ but learns there is another species of elephant indigenous to Asia, she will lose some confidence; maybe Asian elephants can be domesticated. News of hidden generality has evidential impact. When it comes to robustness, vagueness resembles generality more than vagueness resembles ambiguity.