I don't know! If you could try for yourself and see as a player how useful you think they are in practice, that would be a helpful thing to share.
During training, the weaker side never deliberately tries to play bad moves. It's weaker because it gets less playouts, but it is always trained to still do its best. And outside of training there is no actual reduction in playouts. The only difference is that the neural net is told "you are the stronger side" on White's moves and "you are the weaker side "on Black's moves during the search, so it gives a policy, score, and winrate predictions accordingly. You search exactly as usual and the only difference is the numbers that are coming out of the neural net.
So I would not expect a higher rate of "mistakes" than usual. The main difference is the *goal*. Normally both sides try to find moves that can achieve a position such that after that if the rest of the game were played by equal players, the predicted winrate and score will be favorable.
Instead now, white's moves will try to achieve a position such that if the remainder of the game after that position were played by a strong player against a weak player, the predicted winrate and score will be favorable for the strong player, and black's moves will try to get to a position that the predicted winrate and score will be favorable for the weak player.
So my guess is that if you learn from reported black moves, you will likely learn moves that KataGo believes are reasonable ways to try to win if you have a huge lead but you think the opponent can outread and outfight you - such as maybe solid plays and moves that keep pace without picking unnecessary fights, including perhaps moves that give up small amounts of edge that would necessitate sharper play to keep. If you do your own review, you will instead get moves KataGo believes are most likely to be good if the opponent is equally strong. Which could still bias between safe vs aggressive moves depending if you are ahead vs behind - KataGo is partly but not completely score maximizing. And maybe one could try setting it to "aggressive mode" to review handicap games you played as white, once next release is out?
I'm not sure about all of the above - I wrote the code, but it's only been a few days and it's not like I've played a lot with it!
And of course, regarding "weak player" in all the above, KataGo with low visits should still be "high dan++".
