I agree with your speculation about Barrstimeline.
Typically you see them arrest and flip lower criminals to get them to turn on higher ups...
But with 144k sealed indictments, we really dont know much.
The Durham team has kept this quiet.
And Q has said the first arrest will shock people and wake them up (totally paraphrasing), so the first one will have to be a biggie. I think some of the lower level actors (from things Q has said) have been flipping for a long time.