I find that if I use WKWebView with
viewport-fit=cover
and
body :{height:100%}
the height of html body still can not reach the bottom of iPhone X and is equal to the height of safeArea, However, the background-color can cover the fullscreen.
https://ue.qzone.qq.com/touch/proj-qzone-app/test.html
I load this page in a fullscreen WKWebView to reproduce the problem.