Thank you Moritz for you message. If you do an internal linking, it would be register with the page slug (https://yoursite.com/pages/myslug). If for some reason the slug page comes to change, the link will be broken, that’s why to me it would be related.
Regarding why I don’t just add the relative link to my internal page, it’s because it’s counter productive, when you write a post, you don’t want to leave the editor to copy/paste the internal page.
I hope that was helpful.