Not true, you can use something in an untrusting manner. Like assuming everything you send on the platform to be known to the government. Anyone in the USA who uses SMS should be operating like that, for example.
Hmm... if you assume that your government can read your messages but still use the service, then you trust your government to not hurt you based on that. So there is trust.
If, however, you don't send messages you would like to send because you don't trust the service, then it is true that you are not trusting the service, but you are not using it (for those sensitive messages) either.
As soon as you actually use something that matters, you have to trust it. Sending sensitive messages over a system that you don't trust while admitting you don't trust it is... weird.
My point is that trust is a nuanced concept. If you think that it's worth using, then you implicitly trust it enough to use it. Saying "I don't trust it at all but I still use it" is absurd IMHO.
If, however, you don't send messages you would like to send because you don't trust the service, then it is true that you are not trusting the service, but you are not using it (for those sensitive messages) either.
As soon as you actually use something that matters, you have to trust it. Sending sensitive messages over a system that you don't trust while admitting you don't trust it is... weird.