Sure is going to be rehypothecating. Fund structure incentivizes it. See this article on Bitcoin Magazine: https://bitcoinmagazine.com/markets/the-arrival-of-blackrock-bitcoins-first-spot-etf?utm_source=carrot&utm_medium=partner&utm_campaign=carrot_share

The clause about forks shows they want to do stuff behind the curtain.

And yeah, it's a good question! If it's going to be possible then BlackRock shorts would be a hilarious signal to see. My god! Imagine Fink finally screwed over.