Builder not executing sale deed of flat in Thane

I am purchased a flat directly from builder in Thane and carried out agreement for sale in 2021 when the property was under construction. I received possession in April 2023 after building received OC, Society was formed in Nov 2023 but yet to issue share certificate to me. I asked builder to execute sale deed now (June 2024) but builder is not agreeing to execute sale deed even after entire payment of consideration and delivering possession of the flat. He gives following reasons 1. Sale deed is not needed you can ask any one 2. Only 1 registered document i.e. agreement for sale is enough 3. No builder does it in Mumbai/Thane because its not needed 4. Home loan does not require sale deed Question: 1. Is it common practice not to execute sale deed in Mumbai/Thane? 2. Why builders do not execute sale deed of flat in Mumbai/thane? 3. Supreme court judgements clearly say that title cannot be transferred by Agreement for Sale. Does not having sale deed will make my title defective?