I wouldn't say that it's a 'braking system' as such--it's a transmission system that can be used to brake, much as it can be used to propel the bike forward. But I don't want to nit-pick, it's only a question of definition.
You might not define it as a braking system but the article certainly does and implies that the law also defines it as one.
You might not define it as a braking system but the article certainly does and implies that the law also defines it as one.