I noted that as I opened an account immediately after I posted to check out. Thank you datitisev
I also noted that the android app webview code provided is very basic and is not really an advanced version. For instance, it relies on JS / CSS / images files from the website / server instead of providing and use them from the app itself.
I think a faster loading app would use whatever files that are possible to be added to the app itself instead of getting it from the website / server. In this page for example, forum-8451c64f.cs, forum-08315986.js, forum-en-df77f08d.js may be added to the app assets and run from it.
To determine other/all flarum static files that can be included in the app, look into flarum source code or ask flarum developer.