They’re listening to people’s (or their caregivers) explanation of their needs and challenges via chat. They aren’t evaluating them there’s no need to “tell by looking at someone”. I’m sure they’ve been trained with key phrases and words that either approve people for DAS, or trigger further pointed questions to determine if it’s the right fit.
The motivated liars will always adapt. This is why I think the liars are a convenient scapegoat and Disney is more concerned with legitimate users who can be accommodated in some less intrusive way, as well as making the liars have to tell more ‘uncomfortable’ lies (gone are the days of just telling them you have anxiety, ADHD, whatever, or need to visit the bathroom often without further explanation).