Keithl
We strive for continuous decent approaches (particularly in the UK where at the major airports ATC monitor all approaches for compliance)
To achieve a good CDA will mean that you capture the LOC and the GS at the same time. Continuous monitoring of distance to run and ajdusting V/S is required to acheive this.
If you always aimed to capture the G/S from below you would never achieve a continuous decent approach, which would result in increased noise pollution for all.
Capturing a false G/S from above should be obvious given that distance to touchdown is available by DME or ATC 'track miles to go'. (As well as a very high V/S) With modern and slippery jet aircraft it is unlikely that a succesful landing could be achieved from a false G/S.
Regards
Exeng