I think it might be our airport .....ok the rationale is this When I give an instuction like that it is for the following reason .....I would like you to descend when you are established on the ils not before .If I don't give the instruction DESCEND I expect you to remain in level flght till you are given the instruction to descend.Traffic may report established quite some distance from the end of the runway and to clear someone for the ils at that point means what ? descend then to the platform height? ...remain in level flight until intercepting the glide?What about traffic underneath /crossing ..we have a lot of that ..what about traffic which calls just before you report established and then gives it's life history ..would you descend without clearance? I reckon the instruction is perfectly clear ..BUT if you are in any doubt PLEASE ASK FOR CLARIFICATION!!
I think this was flogged to death some weeks ago. Safe flying!!