Here is my experience...I visited branch, my preferred banking RM adviced to link savings AC to payroll without converting it to salary. Weeks later I filled my employer's name in app (pre login)..after filling in details, the landing page clearly mentioned this will not change the account variant but only for existing salary ac holders who wish to change employer's name.
Surprisingly from the next month my account variant changed to premium salary, which I could confirm from smart statement. Then I got call from the bank asking vaguely if I am satisfied with their services and if I need salary account... By this time I changed my mind and said I dont need it. Next month's smart statement reflected my account as regular saving account again.
So I believe the variant changing can be initiated from app which needs to be confirmed by branch people.