I'm pretty sure the 5.5 degree glideslope has nothing to do with "scatter", it is simply for noise abatement (as promised to local residents before the airport was allowed to go ahead), and to miss the rather tall buildings that would otherwise penetrate the lower surface of the approach cone.
It doesn't really matter anyway as far as flare/float is concerned, if you haven't touched down by the inset marker lights it's a mandatory go-around.
Did three years in and out of LCY in the 146, great fun mostly.
Did see one Aer Lingus that floated past the markers, eventually got it down and stopped less than a foot from the end with brakes smoking fiercely. They had to pull it back with ropes tied around the gear legs... fun times (except for the skipper who was crapping himself).