Yeah, in a manual car with the clutch disengaged and a gear engaged (and obviously the gas pedal disengaged), it should brake a little bit on its own. Many people don’t even use their parking brake, unless they’re parking on a slope, because that braking effect is good enough.

But I don’t think, you’d even need this braking effect. You can apply a lot of force to that brake pedal, if needed. I was taught, that if I need to brake for an emergency, I should kick, with full-force, the brake pedal and the clutch.

Not entirely sure, why that’s advised, maybe to avoid having the engine stutter or shut off, but I assume you couldn’t raise the brake amplification much more than that anyways (especially not without the driver being lifted off their seat and losing control).

The amplification is more of a comfort feature, since it means you barely need to move your feet in every-day-traffic.