The whole point of crypto is so you don't have to worry about "trusting" whether or not some entity or another person that has control over your funds will operate in a manner that is in your best interest. The entire blockchain is a TRUSTLESS concept. Having to think about it means, you have left the concept and returned to "normal" concepts in transactions. If YOU don't have the private keys to to your wallet along with zero other parties -- you don't have control. You can say they don't OWN your private keys and they don't NEED TO.. all they need is CONTROL which obviously they have.