I think that may be normal, just based on my experience of having FCW intervene.
The alarm sounds when there is still time for the driver react, but a imminent collision occurence will trigger the active intervention (braking/power cut) without an audible alert, as I recall.
Once, I came upon a car stopped behind a bus on a two-lane road. I observed for a few seconds as I approached and determined the car was content to sit behind the bus, so I decided to pass to the left, into the oncoming traffic lane. Just as I was about to pass the car, it decide it wanted to move in my lane to pass the bus. Fortunately, the car driver looked just as they started to come over, saw me, and dipped back behind the bus, but the motion was enough to trigger the active collision avoidance, braking or cutting power.
The funny part, aside from me not recalling any audible alert, was that just as saw the car start to move my way, my response was to nail the throttle, because I didn't believe there was time to stop, so I decided to get the pass done asap. Of course, the car cut power just as I requested more power, so that was quite unsettling for a second, but I kept my foot on the gas and recovered control quickly.
I suppose that had the car pulled out and kept going, the Giulia would have braked us down successfully, but had the car stopped and I not had room to veer further left, the power cut/braking could have been a collision, I think.
Anyway, like I said, I think active intervention will occur without an audible alert in circumstances of imminent collision.