I looked at the website of the group? behind the project and it seems to be a UI focused team: https://ablaze.one/projects
I don’t really have any gripes with Firefox’s UI and won’t be using Floorp but it’s always good to have more people use Firefox in various ways.
Probably because “installing unsigned code from an unknown source” is a mouthful. Installing implicitly means “from within the walled garden” on these devices.