LG Chem, page-55

@maya.m it was just a thought I had and perhaps I should not have raised it, but certainly the timing seems coincidental. I personally think that there will be no change to the index inclusion and that share price reduction is due to the PLS 'orphan' period before commissioning as Hoots talks about. However to answer you question, the rebalance methodology factors several things other than market cap (some of which I don't understand):
Rebalancing of the S&P/ASX Australian index series occurs on a regular basis. Both market capitalization and liquidity are assessed using the previous six months’ worth of data to determine index eligibility. Shares and Investable Weight Factors (IWFs) updates are also applied regularly. The reference date used for the six months’ worth of trading data is the last Friday of the month prior to the rebalancing.