I don't think that's true. He left around a year ago.
A big pile of money and a limited term could quickly turn a person.
No, but for this year Honda's there full force, as well as RB having resources freed up with the budget cap.
He mainly needs to tell what ideas they missed and to which aspect of the design they can find performance. And if Honda has some advantageous features not present in the Mercedes PU, it's possible they end up in front of them.