I think it is simply a legal negotiating tactic of the lawyers. The one who makes less money always asks for more than they will eventually get (and they know this,) so that when the assets are more evenly split, the one who makes more will feel better about what the other DIDN'T get. The only difference here is that People magazine publicized it.
If you read ALL of the article, it also states how Nick sited the separation started in DEC, not Nov. By doing that, he is already giving up $1 million. They publicly announced their separation Thanksgiving weekend, another well calculated tactic, and one Nick would hardly make such a crucial a mistake on the date about, since he spent it without Jessica.