Say you are playing a tournament for money. In free tournaments you probably wouldn't care. You defend 3NT and your partner leads a spade, declarer winning the trick. You win the second trick, play another spade, declarer wins again but now you have established spades for your partner. Two tricks later, your partner disconnects. TD replaces your partner and new partner hops on. You are now aware your new partner has no slightest idea about play of the hand. He sees bunch of low spades in his hand. You are well aware 3NT goes down if he keeps them, and it makes if he doesn't. It's obvious this makes quite a difference on your tournament placement. Do you think it's ethical to tell your partner that his spades are high? Do you think it's ethical to review the play to your (new) partner? If yes, to how many details [does it include partnership agreements...]? Any other solution you could suggest?