That's the problem. It is evidence of what that person observed. Nothing more. We don't always observe things correctly, or interpret those observations appropriately.
Your anecdote about Dominion accessing a machine remotely is susceptible to that framework. That's fine that the person testifying believes that to be true. Which terminal? What representative of Dominion? What was the actual problem? Was there another observer to corroborate? There are more questions to be answered before that observer's testimony crosses over into persuasive evidence.
Some of the least reliable admissible testimony is that from eyewitnesses. That's why cross-examination exists.
And, frankly, that's why investigations look REALLY hard for physical evidence and any corroborating testimony.
