Completely agree. It's foolish to do anything but praise him

The more that he praises Jack and "cements" his legacy as a great leader, the more likely Jack fades away feeling that his work is complete

I've taken over from some pretty incompetent assholes but you'd never know that from my speech I gave about them. And everyone else in the audience knows too. Let the guy go away thinking he was great and disappear from my life.

If you are almost immediately, even subtly, criticizing your predecessor, the more likely they are to want to respond or stay involved. This is basic leadership politics.