You seem to have got it all wrong. Not only are you losing your Savings bank interest income if you prepay you are also paying the Rs 120 on your foreclosure. In effect you are losing Rs 150. In case of Zero EMI you will only pay the GST on the interest and not interest + GST. So, interest of Rs 150 will mean .18% x 150 = Rs 27. In effect you will be losing foreclosure charge + loss of savings account interest - GST on EMI interest = 120 + 30 -27 = Net loss of Rs 123 if you foreclose.
I have yet to see how it pans out, but I went through the T&C. It stated that outstanding interest will not have to be paid in case of foreclosure. Since the interest is already discounted from the upfront price, with foreclosure you save on the interest and GST that you will have to pay if you continue with the EMI.
So, there is indeed a benefit in foreclosing the loan early on,