Ah, I see what you are talking about now.
I went to the helpers documentation page and copied/pasted their example code into a new fiddle. I then renamed the "isSelected" helper method to "selected" (so as to match a property on the "scope"). I can confirm that the the "helper" has higher priority than the "scope" within the view.
Please note that this is undocumented and is even confusing when reading the very simple code in the fiddle. Your code my break in the future... and at best will be confusing to newcomers. Make sure you include a comment in your template which says "see helpers first".