I believe that the action does reflect Jobs' ego in the following way.

Namely, his belief that CEO == company.

Jobs would never take the view that the action of the CEO of ATI is actually one bad actor acting alone which doesn't represent what ATI wants as an organization, and is unfair and damaging to that organization and all of its employees.

The reason he would not take that view is because then he would not be able to believe that he is the single most important thing at Apple, overshadowing everything else.

If the leak had been the responsibility of some rank and file employee at ATI, with appropriate action taken against that employee by the ATI CEO, it is likely that Jobs would likely have reacted differently, because it then would not longer be seen as a personal matter between him and the CEO, where the corporations are just pawns in a game of teach-you-a-lesson.

For violating an embargo and publishing a press release announcing products of another company that hadn’t been debuted? What “non-dick” response do you think is appropriate against a prospective partner that violated clear guidelines that defined their partnership which basically included “#1: Keep your mouth shut”, exactly?

Going scorched earth was kind of Steve’s thing.

He was, but this incident wasn't an example. That's a righteous punishment for an infraction like that.

They unilaterally issued a press release about Apple's upcoming release.

That's kinda a no-no for partnerships.

One word: "Courage"