Builder in Noida asking me to carry out "Agreement to Sub Lease" instead of Registry

I have recently taken possession in one studio apartment in Noida for which the builder has advised that OC/CC has been provided by the Noida Authority. However, there are still a few towers in the complex which are still under construction. Also, I have a no dues certificate issued by the builder. Siting a UP RERA office order dated 16.09.2019, the builder is after me to carry out Registration of Agreement to Sub Lease (ATSL) of my flat, which will be conducted by some law firm. This ATSL is to be registered between the Builder and the allottees. I will be required to pay the stamp duty to get the ATSL duly stamped and registered. They also state that the Final sub lease deed will be registered in due course on Rs.50 stamp paper only. They say that at present, registry (sale deed) is not being carried out by the Noida authority and this is a work around to make our possession legal. Also, as per a RTI reply, there is still an outstanding amount remaining to be paid by the builder to the Noida authority to the tune of about 370 crores. What I need to know is whether this ATSL will in anyway put any liability regarding recovery of dues by Noida Authority from the builder to the allottee. Also will it in any way put the onus of maintenance on flats from the builder to the allottee.