The bank is lending you the money, and they have to take proper precautions like verification of title to your property and such opinion from their counsel. One may be having title deed of a property from 1950, but having title deed is itself not complete legally, as they have to see the link transactions as to whether the seller is having a good title to sell property to you. In case the seller is having defective title , he can not deliver bonafide title to purchaser.
Obtaining of EC and certified copies of link documents is most necessary for every purchaser. If you have not obtained, you can obtain the same from Registrar within a week and the procedure is simple. When a Public Authority is having well laid down norms and stipulations since centuries, any violation amounts to their negligencce.
As a good borrower, submit those certified copies in your own interest. Bank Manager is not having any discretion to waive any documents and he has to go as per legal opinion of Bank's legal counsel (Retainer). You may try from private or LIC HFL if you think that banker is harassing you.