They wouldn't have to. A simple workflow could be as follows...
User registers for DAS with a developmental disability that has been concluded prevents them from waiting in a queue. Their name and details go into the computer. System can identify they are an employee and they get flagged.
Later, a second system reviews all employees who qualified for DAS and compares their work history and accommodations. If by some pre-determined rules of intersection of key data points happen, you boil the record up for manual evaluation. Someone in HR can review by inspecting the person's responsibilities, documented accommodations or reported limitations, and comparing with the DAS request.
Disney's purpose isn't to deny them the DAS when they apply - you don't want to deny people something they may need. Instead you post-analyze the data to look for irregularities, screen, and bubble up ones that methodically that seem suspicious. Then you assess, and either dismiss the alert, or take some other action of your choosing.
Point is, you make it an employee issue - not a denying accommodations issue. If someone ultimately is lying to get DAS, they put their park privileges and employer/employee relationship at risk... you don't try to screen them out of getting a DAS. You leave the r