I think you are reading too much into this.
The company was clearly unhappy with Ziv.
I agree with you that it's confusing in one breath to read Ziv resigned and in the next that he was terminated for cause.

What I think was that the company was going to fire him. I think there was some negotiation on how to frame the dismissal hence the confusion.

I think what you said is very true about resignation versus termination.
So I believe the company had just cause to fire him but exerted a little pressure on him to resign so he has very little recourse.

What is confusing is the fact that both termination and resignation are discussed in the 8k.

That's why I think this was all negotiated so there would be little pain for OWCP.