The thing that strikes me is the disparity in length. I think a lot of people don’t realize how hard it is to write succinctly. Jobs was (is?) probably under-appreciated as a writer.
Colligan was correct such an agreement would be illegal and could have just stood on that.
Colligan was putting down what had occurred in writing so that the details of what Jobs had said would be a matter of record should it come to a lawsuit down the line.
This is a common - and highly useful - strategy if you've just been in a meeting where things have been said that you were uncomfortable with.
Being succinct would have defeated the purpose.
This is a useful strategy to employ in all kinds of situations. A dated note written shortly after the event is going to carry more weight than recollection later. An e-mail sent to the other party that they have not contested the understanding of is going to carry more weight than just a note.
And if, as Jobs did, your other side responds, you now have ammunition for any future lawsuits.
EDIT: Creating a paper trail is a method to take note of in other contexts too. Your manager at work asked you to do something unethical? Summarise your understanding of the conversation in writing and ask if you understood it correctly (a lot of the time, the request will magically become a misunderstanding).
Jobs tries to bully and threaten a smaller company into signing an illegal agreement and all you have to say is how great of a writer he is because of how few sentences he wrote?
Did we read the same emails? The Jobs email felt like a toddler's emotional response, whereas Ed's was thoughtful, considered, while still sufficiently short and to the point.
Colligan was correct such an agreement would be illegal and could have just stood on that.