By maintaining the partnership with a foreign partner, they can get fairly advanced manufacturing IP and knowhow without having to R&D from scratch.
Indian companies don't have the need for 100% IP transfers like China because most have had shared IP partnerships with Western countries for generations (all the way back to the British Raj), nor have private sector Indian entities ever faced sanctions similar to China or Russia/USSR in the 20th century.
This also helps adjacent Tata Motors, as they were severely impacted by the chips shortage and the battery shortage (for their EV division), along with Tata Advanced Systems (the defense contractor) who need commodity chips for a number of it's armament SKUs.