> after I indicated that I don't have vocal cord paralysis, the survey was over

They're not collecting information from people without the condition.

This is simply their way of getting rid of people who shouldn't be filling in the survey.

I think it's actually a reasonable UI decision. They could have done it one of two ways:

1. Have the page say, "Fill in the survey ONLY IF you have the condition".

2. Anyone can fill in the survey. But the first question determines whether you are a candidate or not.

They chose #2.