Agreed on all points, with one caveat: ORs sometimes reflect what the writer wanted to have happened, not what actually happened.
A post-Civil War example is Terrys reports of Custer's defeat at Little Bighorn. His first report seems to align with all known facts, while the second- written days later- appears to be simply CYOA.
Unfortunately, because of communications at the time, the second was received before the first, and made it into the newspapers. Many- including both Sheridan and Sherman= made statements they later regretted and had to revise.
Sadly, even with the best of intentions, there is no way to overcome personal bias: it is what it is. The reality is once an event occurs, all subsequent attempts to describe it or record it are subject to bias.
A good historian, though, is one willing to work, to do the tough research to find and evaluate the earliest, least biased, primary sources, not simply- as all too many writers do- copy someone else's speculation.