Page Functions doesn't work in WebUI

I tried using multiple page functions (PageGetPrevious, PageGetFocus, PageOpen), but I keep getting the error message: "WinUI pages are not available when project is setup for WebUI."

I am wondering if these page functions are only applicable for WinUI? I tried webui::OpenPage, and it works in the WebUI. Is there another set of page functions specifically for WebUI?

