Why is PHPStorm suggesting functions that aren't available in the current language level? Follow

I'm trying out PHP's built-in XmlElement object, and PHPStorm gives me a suggestion for ->getChildren(), but when it's added, it then shows a red underline error, upon which hovering shows that it's only available for a future version of PHP, which I'm not using.

Why is the editor even giving me the suggestion to begin with? This is frustrating. It shouldn't be showing pointless suggestions.

I think hasChildren is also not available to the version I'm using, which I'm guessing why it's in red, but why even show this?

Either I didn't notice before that getChildren was red, but I don't remember it being highlighted like that, and there's no clear indication anywhere in the suggestion box that it's not actually available to use.