You see technically it should be but once you block and generate a new card they don't give a choice to go virtual only (At least not until two weeks back), maybe it's in the works, maybe they assume why someone would not opt for a free physical debit card, either way, you can get the physical card; burn it and voila you now have a virtual-only debit card
cheers. Maybe that's the reason Indus backend developers didn't write the code for a virtual-only card