Yes. Because of how your driving score is calculated, any sudden braking will reduce your driving score. This includes braking suddenly to avoid a crash.
This doesn’t mean you were ‘wrong’ to brake suddenly. Sometimes it really is unavoidable - but our app has no way of knowing.
The good news? Your driving score is an average of all your drives over the whole period of your policy. So as long as you drive smoothly most of the time, it’s unlikely that any single event will have a big impact on your driving score.