fixed asset 'What if' function, does it only give right forecast if period closed after adjustments

We have been trying to use the fixed asset 'What if' function. Our Service Delivery want to use it after draft depreciation has been run but not with the current FA period closed. They want to use it this way to show their customers the likely depreciation amounts to the end of the asset life before they commit it to closing the current period,  and thus before final depreciation is run. I think they want to do it between draft and final depreciation so that they can carry out additional unplanned depreciation if need be for their customers, before the