My two cents worth!
Don't know Woltz then why all the deception?

He might have been mostly honest with Michael about how the meeting with Ola went but everything before and since was devious, dishonest, deceitful and he was quite the deep thinker, coming up with all those lies, lie after lie, he was feeding Michael

He also withheld information even after the first senate hearing

"I'm your older brother Mike and I was stepped over!" was no doubt what took Fredo to betray Michael.

I reckon the smart -- not dumb Fredo considered exactly what he would end up with, something good for him the Donship when Michael was dead--and Fredo knew it without being told, anything specific.