jigsaw, exactly. You'd have a holding page that's made up of some fixed content and some content from an SSI. On my site the left column, right column and even the nav bar are SSIs. So despite the fact that my pages are static pages I can easily effect a sitewide change of header/footer/navbar/column just by changing the relevant SSI. (That's what I did recently when I added a link to these forums in the nav bar. It took me less than a minute)
If someone else is calling an SSI page from your site (like "hotlinking" an image) it would show up in AWstats as a page view because it is, after all, a htm page. But as it's your holding page that has the Analytics code, GA doesn't know your SSI was called and wouldn't record that as a unique.