is_feed() before template_redirect()?????

i have come across a bug in one of my plugins

https://www.wpultimateplugin.com

the problem i have is that when a user opts to use the title rewrite setting the rss feed title all become the blog title??

the way the plugin rewrites the title is like this:

if($options['title_rewrite'] == 'Enabled'){
   add_action('template_redirect', __NAMESPACE__.'\before_header', 0);
   add_action('wp_head', __NAMESPACE__.'\after_header', 1000);
function before_header()
   {ob_start(__NAMESPACE__.'\change_title_tag');}
function after_header()
   {ob_end_flush();}
function change_title_tag($head) {
   //Replace the old title with the new and return
   return preg_replace('#<title>[^<]*</title>#', '<title>'.seo_title().'</title>', $head);}}

so i access the head element from the page and format the title using another function seo_title()

the new function has a !is_feed() check but id doesnt seem to be working??

is this variable even available before the template_redirect() as i think this is the issue.