No, it’s actualy work under Nginx, I use nginx and this awesome plugin work properly.
Maybe you should put this code within your server block file.
rewrite ^/sitemap(-+([a-zA-Z0-9_-]+))?\.xml$ “/index.php?xml_sitemap=params=$2” last;
rewrite ^/sitemap(-+([a-zA-Z0-9_-]+))?\.xml\.gz$ “/index.php?xml_sitemap=params=$2;zip=true” last;
rewrite ^/sitemap(-+([a-zA-Z0-9_-]+))?\.html$ “/index.php?xml_sitemap=params=$2;html=true” last;
rewrite ^/sitemap(-+([a-zA-Z0-9_-]+))?\.html.gz$ “/index.php?xml_sitemap=params=$2;html=true;zip=true” last;