However, the doubt rose from the fact the glidepath leads you to the aiming point, 1000' mark. Since the threshold is displaced, now the glidepath leads us to the beginning of the displaced threshold.
How do you know this? Is this a 'temporary displaced threshold'? If it permanent it might be the VNAV is taking you to the GPS coordinates of the RWY TDZ. It is something to ask your performance dept and they will pass it on to the FMC data base supplier.
If it is a temporary displacement then your Ops dept should issue crew guidance.