That looks almost identical to the "sitemap" template ST has built in already.... unless I'm missing something?

Yes, it's very similar. The things I added were: (a) display page body text prior to start of sitemap (with the ST sitemap template, it doesn't display any text you manually type into the sitemap page body field, hence `the_content();`), (b) add category description beneath each category label, (c) get rid of bullet points and comment count, and (d) style the date in smaller monospace font so posts are lined up neatly.