This is the only real worry I have with spot ETFs of crypto. If the institution loses keys, or gets hacked, etc (insert other technical glitches here), you stand to lose your securities.
No one worries about their shares of Enbridge or Walmart getting sucked through a vortex of the black hole.
Institutions can and do mess up in many ways. This is not new to crypto. The original intent of crypto is that everyone would hold their own private keys. It's like having cash in your wallet. You are responsible for it. But the advantage you receive is that it is technically impossible for anyone to take it so long as you keep your private keys safe.