That's not really how it works. If it was a scan and 5 seconds of wait for return of data, why do we have to hold down the scanner button? Seem to be a charge of some sort (if it isn't why don't we get a partial scan if we let go early?).
The ADS was an insta-win button, held down for 5 seconds to give us a populated system map. After that we were left to our own devices.
The FSS appears to be a set of busywork set up after the honk returns a bunch of energy/frequency signatures for us to play with. If, as other have stated, we try to use it in the exact same way we used the ADS, it just results in a lot of busywork for the same outcome. But it can be used a lot smarter than that.
Ideally we would have something in-between the two. Plenty of suggestions here and elsewhere as to what, without having to resort to historic non-mechanics.

S