The reason why it's asked for is because people have multiple tabs open, often dozens, and they want to find the flarum tab quickly and so are looking for the flarum site title, e.g. Flarum Community.
The problem is that this part of the title often gets truncated by the browser so all they see is the first part "Change the browser...." and might not recognise it.
Obviously a unique favicon helps, but having the site title first in the window title is the most obvious UI design.