And looking at this further, what I initially thought was a result of an inconsistent example now looks like an error. The <base href> should be referring to the published URL of the document, and not to the internal filepath of that URL. In short, it should refer to the same URL as that by which you refer to it in links -- the friendly URL.
So, based on your other examples, I believe it should read
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<base href=http://example.com/seo_page.html />