I've worked on medical devices. As a techie, what surprised me more is not the lack of trials for new devices. It's that for software (and other kinds of components), it's often acceptable to have black box testing to certify a component as functional.

This means basically saying "I pressed a button and the thing did X". That's the test. No need to understand how that works, or provide any more technical documentation or specs, or record system state or variables, or do anything else. Press button, it does X. That's good enough to be certified.

The reason for this is simple enough: sometimes the thing you're using is proprietary and its manufacturer/vendor simply won't give you anything else to certify it. But this black box testing is even used for open source software and components. It's like a short cut you can use to cut through a lot of the testing you could have done. I imagine this will remain standard practice as the "AI" companies push their hallucinating dreck and unexplainable magic into the medical device space.