Questioning should include a trail of documentation to support their statements thus winnowing out the chaff from the grain. Without documentation it’s just opinion or hearsay
I agree that we need some documentation of some essentials...like stand down orders and all orders sent through the chain of command. That is a must!
I do think that hearsay should be allowed though, as the content of phone conversations would be a hard thing to have a record of, etc.
Your point is a good one and probably why the emails are so important. They back up what is being said in testimony.