I take everything Roger Stone says with a huge grain of salt. He was predicting that the RNC would refuse to nominate Trump. He predicted massive street rioting during the RNC convention. He’s predicted all kinds of stuff that never came about. This prediction is probably a little more likely, but I’m still skeptical.
I’m not skeptical at all the Mueller will go for processes and technicalities when an actual crime is absent.
Stone is quite right on this.