I think KE upgrades on oversold flights based on fare class.
At least that's what the checkin agent told me.

Upgraded only once on a higher economy fare class to business but was served economy food.
Never been upgraded because I was Morning calm.

I think KE's morning calm is quite useless.
The only real use is for the lounges but now with credit card priority pass etc, lounges are not an issue.
Besides, KE lounges arent the best anyway.
Not missing out if u dont go.