It's more about culture than neurotype. There's nothing in human nature itself or in human instincts that says "people will feel uncomfortable when refusing something that a stranger of equal social rank is asking of them, unless they have been provided with plausible deniability". It's a feature of our current (Western) culture. And since autism tends to come with issues relating to general intercultural competence, it's no wonder that someone who's autistic would have trouble picking this up. But so would any non-native in the relevant cultural context!
This seems like a reasonable interpretation. People from other cultures may also be excused from cultural norms to some extent as people understand that they don't have the context. And I've definitely gotten very good at politely diffusing situations where I've accidentally crossed social boundaries (I have more problems when I take moral issue with the social norm, and thus am unwilling to go along with it).
