The only differences I can see are an added line break in your code:
<block type="page/html" name="root" output="toHtml"
template="magentotutorial/helloworld/simple_page.phtml" />
and the absence of a closing / in the tutorial code at the same line.
<block type="page/html" name="root" output="toHtml" template="magentotutorial/helloworld/simple_page.phtml">
Both examples seem to have two opening <block> tags, but only one closing </block>.
Aha - one of them is self-closing in the second example? (I’ve no idea what I’m looking at; I’m just fairly adept at spotting typos. )