Nokia is not handling system ui. Its handling by google. But call recording is important application and other companies like Xiaomi its already given manual call recording options. So why nokia is not giving options..
"So why other company give call recording options in indian vairent."
The keywords in your post are "Indian Variant". AFAIK recording calls isn't illegal in India which is why the option is available. The Nokia 8 is available worldwide and HMD probably don't want to create a separate version for India.