Right now for the host they're the same button as ready, which means that if the host wants to un-ready-up it's impossible. Often times people like to rotate host between each other and out of habit a player (who became the host) might want to unready and then whoops! game started.
The whole start button should be a separate button from ready/unready. This would solve all of those accidental starts.
The whole start button should be a separate button from ready/unready. This would solve all of those accidental starts.