Hey there, I took a look at your itch profile on desktop and the embed you have right now seems to be working fine, with the white loading bar visible. What you may be seeing is that your browser has already cached the files, and may only be sending the progress event for 0 or 100 and skipping most of the loading state on repeated visits.
Viewing post in (Unity) Better Minimal WebGL Template comments
The template isn't actually responsible for any of the progress events, it just listens for the progress from unity. If it's behaving strangely on other browsers, it may be an issue with how unity is loading the files and firing the events.
If you want to force it to go slowly locally just for testing purposes, most browsers have a network tab in their dev tools which allow you to disable caching and simulate slower network speeds.