Blackrocks application could be full of clues to the Index theory..
Page 58
'There have been several forks in the Bitcoin network, including but not limited to, forks resulting in the creation of Bitcoin Cash (August 1, 2017), Bitcoin Gold (October 24, 2017) and Bitcoin SegWit2X (December 28, 2017), among others.' 
Page 24 of BlackRock ETF application says they can choose any fork of Bitcoin for their ETF regardless of spot price..
Thet could retain any future forks split coins and make bank big time..
Interesting stuff