When "Add no selection" is selected, Dapresy will add a category "No selection" to the filter options. Here you see where "Add no selection" is selected:

And here you can see how this looks like in the filter:

However, this "No selection" is not behaving always the same when using normal filters versus dynamic filters. 

Normal filter: When you give report users limited access rights to that filter, for example to only Region A and Region B, Dapresy will automatically check the answer categories instead of adding the "No Selection", see example below :

In case you use dynamic filtering "No selection" is still added, even though you have just access to only those two regions. In this way, Dapresy dynamically calculates what "No selection" should contain (in this case only region A and B).