Earlier quoted context omitted.
Those are distinct from my concern. In your scenarios, I have trusted you to keep the conversation secret, and you betrayed that trust. My concern is about giving messages in an automatic fashion to a third party, which I'm completely unaware of and have no way of making an informed decision about. The third party could be breached (they run an online service, which is much, much easier to attack than some dude's iPh…
Just ask your conversation partner? An Element bridge is just a Signal client hosted on Element's infrastructure. Them using an Element bridge is no different than them using an extra device you didn't know about. That device could've well been insecure, or shared by many people, or hosted in the cloud. If you care about this, you should ask.
In the end it isn't a huge deal, as most conversations are extremely innocuous, and those I care about I'll take the time to verify. But after all the trouble to proselytize Signal, I get nervous about large public projects that could, in my opinion, strictly reduce the security of my secure messaging system.