can’t see an issue with the code – maybe worth testing the shortcode they provide on a standard Page with children. If that works then the code is good and the problem is with the child templates you have defined.
May i ask whats the need for the faq template ? Does it differ from a standard page
good question about the template,
I was going to ask, can I simply copy the template for pages (page.php and content-page.php) into my child theme. So not rename them to page-faq.php and faqcontent-page.php.
Then I can put the code in them and it will override the template in the parent theme?