Ann: S&P DJI Announces June 2020 Quarterly Rebalance, page-7

For all the hype getting included or excluded from a particular index does very little for the SP. For example if a fund is based on the all ords (ie a fund representative of the weightings of the all ords) and FBR drops out, then that fund will sell its weighting in FBR. But FBR might have only been 0.2% of that fund. So if that fund was worth $100m then it might sell $200k of FBR. But it won't dump them today, it might have preempted the removal and sold already or will sell over the coming weeks.

Today is going to be total carnage, just watch companies that are being added to and removed from the ASX300 and you'll see little difference in their performances.