WordPress updates the post/page modified time only when you save/update the post/page in the editor. If you have shortcodes or blocks that create dynamic content (ie. returning content from queries, files, feeds, etc.), the WordPress post/page modified time will not reflect these dynamic changes.
The Solution:
The JSM Accurate Modified Time for SEO plugin monitors the post/page content for changes and updates the WordPress post/page modified time as required.
If you use a social and search optimization plugin like WPSSO Core, Yoast SEO, The SEO Framework, Rank Math SEO, All in One SEO, etc., the Open Graph og:updated_time and article:modified_time meta tags, along with the Schema markup dateModified property, will show accurate modification times when shortcodes or blocks updates your post/page content.