add_filter( ‘the_title’ gets through this if statement twice

I am using the accepted answer shown here: Apply the_title() filter in post & page title, but not in menu title

For some reason, the code is getting through this if statement twice:

if ( ! is_admin() && $  post instanceof WP_Post && ( $  post->post_type == 'page' ) && in_the_loop() && is_main_query() ) { 

I am already using the pre_wp_nav_menu and wp_nav_menu_items filters as shown on that answer.

What would be making this code run twice please? Or how would I debug to find out what is calling it and letting it through the if twice?

(When I use debug_backtrace() is shows apply_filters line 212 in plugins.php both times but I’m not sure what to do with that info)

Sorry, I would ask as a follow-up on the posted question, but I evidently can’t comment yet.