Your method would increase complexity while making the pact harder to hide, and keeping down wages is a nice side benefit. Keep in mind people generally don't start off trying to do overt wrong.
If anything I might buy the argument that Jobs was a huge control freak and that's what drove him to do this more than anything else, but how do you think this went down.
Jobs really didn't like having his engineers poached because it disrupted continuity. So he said to himself ... what am I gonna do? what am I gonna do? Offer 2x whatever Google is offers? Noooo ... that would never work. I need to call up Google and threaten a poaching war?
I'll go with Occam's razor. The simplest explanation is the best.
And please note, I'm certainly not defending any of this behavior, just examining possible motivations.
(And well that's how exploration of different narratives goes, it's a constant struggle compared to simply picking from the limited two-sides-max of mainstream press)
And an ignorant, unstructured, or illegal approach to benefiting yourself often hurts other people.