The 'managed' s_code will be loaded in a separate script call when the page loads. DTM doesn't modify anything with your managed s_code, but simply does not load it when needed. Here is a screenshot of what I am referring to:
[img]Screen Shot 2014-06-12 at 10.13.31 AM.PNG[/img]
s-code-contents... is the file that gets loaded dynamically for your analytics tool that contains the 'managed' s_code for your analytics tool.
So, the purpose of specifying the s_code is just the same as legacy analytics implementation. It is just like include s_code.js on your page, but now can be managed a little better.