How to customize native modal for safari web extension in iOS?

I've successfully built a Safari extension for my app, but I've noticed that some applications have a slightly different style when opening the native modal through the "aA" button (I'm not referring to the injected cloned modal, but the "native" one).

There are two major differences I observed: the first is the header color, which is gray instead of the regular white, and the second is that this modal doesn't open in full screen when dragged to the top, unlike the regular one. I'm interested in knowing how they achieved this. I couldn’t find any information about it anywhere on the web/docs. Thanks!