The two supposedly premium cards that I have as LTF are DCB and Eterna. I both cases I had applied for lower variant and did nothing to get an upgrade. I was being offered AU Zenith LTF, but gave it a pass. Also have no plans of upgrading IDFC Select to IDFC Wealth.
For SC Ultimate I had to try hard to get a limit increase and then apply (despite not being LTF)
Magnus was an easy application and approval process (again not an LTF)
So all in all, a mixed bad and mostly luck!