Drop down does not clear not selected value

Drop down does not clear not selected value

I created a simple Yes/No drop down field on a form (see attached screen shot). The default is set to "No," so if an appointment is what we consider value add, the sales person selects "Yes." 

In all of the drop downs I've used over the years, selecting something other than the default clears out/negates the default value. In this case it isn't. 

Interestingly, this field works as intended on the Zoho CRM app: the sales rep picks yes, and "No" goes away.

So I believe there is a problem with the functionality.

I look forward to your response.

John Galich