could be but as an example of what I am thinking ... SP Mueller did not need Manafort to "help" Mueller's case ... all SP Mueller needed was the evidence which presented the case itself.
Of course it could be since Mr Trump does not use any documentary applications except twitter (I am excluding telecoms as I don't know how long phone server logs kept), it could be necessary for eye witness accounts. But then Manafort is a proven liar (would he lie to save his skin?) and of course we have the narcissist who compulsively lies ...
I am not so sure everything is as it appears and as clear cut as many believe it is.
ignorance is the enemy
without equality there is no liberty