Is separate Partition Deed required to be prepared for Development Agreement

We have inherited a property from our ancestors in Kolkata. After years of living in the same we brothers have mutually agreed to give the property to a developer for redeveloping the same. After redeveloping the property we have decided to take some apartments as some cash from the developer in lieu of the developed property. For this we are entering into a 50:50 share joint development agreement with the builder. The inherited property has a will and a registered probate has been taken on it to make it legally viable. Now the developer while preparing the developing agreement, is asking us to make a partition deed for the allocation of flats which are going to be distributed to us at a later date. As I understand that I am giving an undivided, encumbrance - free property to the developer to develop. Also the share of the stakeholders are as per the will document as prepared by our grandmother and mutually agreed via a Memorandum Of Understanding amongst our brothers. I have a feeling that the builder is trying to pass on the burden of registration charges to us. I have an understanding that the development agreement itself should contain the allocation of shares amongst the stakeholders mentioned in it in the Annexures and the same shall be registered in a court of law by the developer only Require your guidance in this regard as soon as possible