Ah, my mistake Brandon. I'd disabled all BWP plugins remotely and re-enabled WP SEO expecting the sitemap to function as it was previously enabled based on the first site I tested. This is not the case. I had to manually visit the other sites and click the XML button to get the sitemap to regenerate (or clear any redirects).
Oh, and on a couple of sites I had to (as you suggested) disable and re-enable the sitemap feature in WPSEO. htaccess was clear of any redirects, possibly some cached code / redirects. That fixed it. Thank you for that push.