Even if they act in good faith picking the correct chain, I'm missing details on what happens to the value in a possible Fork chain. When the BCH Fork happened, the value of the Forkcoin varied, but could have been sold for 10-20% of the Bitcoin value. If they keep that instead of sharing it with the ETF investors, it just adds to the list of reasons to keep your own keys.
This is from Blackrock's filling. I assume all other ETFs have a similar take? It is a sort of a disclaimer. "We cannot guarantee that this is the most valuable fork if it splits". Of course you got to realize that all of these are under US jurisdiction, so the government could step in and say, "make this or that fork as the legally abiding one". And there you have it, now all exchanges and miners are forced to mine whatever UScoin fork. This is the problem with the ETFs. Back then we had separate entities as big holders, now all these ETFs will centralize a big stack on the same hands. The only hope would be that big whales dump on UScoin fork as everyone would get a split of each other coins on both blockchains post-split and cause a crash on USfork. But you would also need to get miners out of US jurisdiction reach. I know companies like MARA are expanding overseas but they would still be subject to US jurisdiction, and im not sure if UAE would be any better (they are doing some business there).