This was my opinion, which seems to be wrong in hindsight. See the next post from @dtyxg for why.
This is because NSE introduced pre open session, which calculates the equilibrium price at pre-open, based on matching orders, even when there’s no trade volume.
@dtyxg Practically, it all moves on it’s own, before the underlying moves and based on whether there’s interest/supply/demand/jane street. “We don’t know what changed. What caused the spike. Let’s just call it implied volatility for the math” Also it won’t move without a trade. So if volume is 0, there shouldn’t have been any change in price, at least before Dec 8, when NSE introduced preopen session.