Referencing a CMS Page within another CMS page

I’ve got one website that, within a CMS item, I can reference any main page or CMS page from the site. All of my other websites though, I can only reference what’s considered “main pages”. I’m curious if anyone knows of a specific setting around this that I’m just missing as I’ve been pouring over the different sites. I’d like to be able to reference the pages rather than just link to them so they stay up to date when URL’s get changed in the future. Not sure if a read-only site is helpful here as I think it’s probably just a simple setting I’m somehow missing, but I’ve attached examples below and in images. If any further clarification would help, just let me know. I’ve seen a few other people ask similar questions, not sure if this is what they meant though so I’ve opened up a new thread.

Site I can reference any page or CMS Page

Site I can only reference a specific page