This is something that comes up often. I don’t recall right now what the decision is or was or even if the developer has commented on this. I do know that there are all kinds of things that you can link to in WP that are not represented by a “Post” or “Page Link”. I use the setup you’re talking about all the time. There are times I simply use a text field so that the editor can put whatever they want in the link field, for example mailto:[email protected] or allow them to enter /root/relative/urls/ If the developer extends the “Page Link” field to include a radio button to select a page or enter a URL then others will request that he extend it to do other things as well.
There is also a difference in how the value is stored. The value stored for a Page Link is the Post ID where the value for the url is a text value. All ACF fields have one thing in common, each stores only a single type of value and what’s returned is determined by the other settings you give each field. There’s no logic needed to determine how to get the value, only how to display it. I think this is actually the main reason why this has not been added even though it’s been requested several times.
