794 Hart St, is there really a j51 abatement?

We are all set to go to contract on a unit at "The Knick". While the advertised j51 abatement has been approved for the other 2 buildings in the develoment, the 794 building abatement has not been approved. Is it common for buildings to advertise an abatement that gets denied? What can be done after the contracts are signed and you are stuck with the full taxes? Does anyone have any insight on this particular building? How long can it take to get approved? We love the apartment, and are trying to decide if it is still worth it if the abatement does not get approved.