I am testing Blocs 2.4b4 right now. I built a simple 2-page site and filled out the Page Title and SEO fields on both pages, and then I exported. I went through all the folders exported but I do not see a file named "sitemap.xml".
I fully understand there are free online tools that generate sitemap.xml, but having such built into the web design tool is a big help. Right now I use SoftPress Freeway Pro 7 and I use the SiteMapper action to auto-generate "sitemap.xml" for me. I set the frequency and other settings once in the Action settings, and then after that I don't do anything. I just Publish and the xml file gets uploaded. I think Blocs needs the same.