How to use {{#has}} helper as a switch

Well I was absolutely mistaken!

I just tried it on the Casper theme with one of the default posts, and it worked:

{{#has tag="Fake Tags"}}
  Fake Tag
{{else has tag="Getting Started"}}
  It works
{{else}}
  Neither tag
{{/has}}

Let’s try to debug your issue - is your code working with the nested condition option I mentioned?