The usual reason for a displaced landing threshold is to preserve the required obstacle clear approach surface according to the runway categorisation. For some runways this can involve a significant loss of declared LDA.
The declared distance should be used for operational calculations. The intention is that the aircraft doesn't land short of the markings and the pilot exposes himself/herself to censure if doing so leads to any problems.
The opposite direction TORA may well extend into the area prior to the commencement of the declared LDA.
The party trick with the Sportstar was to land as short as possible and make the first taxiway on 17L
I have no idea what the Sportstar might be but that particular party trick is a good way to end up embarrassed in the event of a cessation of noise .. yes, I know, we all did it as youngsters.