the new mount was probably not arround when talwar was designed, orginal mount for a-190e is supposed to have rcs reduction as well according to the manufacturer.

The A-190 on Talwar is the first application of the new lightweight 100mm gun. Considering how quickly and cheaply these ships were built for India, and that India is licence building the Oto 76mm and is building P17 in country, the IN may not have wanted to wait for the A-190E and/or have considered the price difference too big.