Funny how we both ended up in the PHPBuilder and CC forums.
Anyways...
From what I understand, with include your page is read and executed before the output is displayed.
So, even though you tell it to display before you unset it, since include is being used, the page runs (unsetting the variable), then runs again and gives your output.
I read somewhere, dont know where, that using include actually runs your page 3 times before the actual content is sent to the browser.
Someone please correct me if I am wrong.