OK, to talk about this kind of play in general, let me start with losing sente. A losing sente is quite simply a move that is made with sente that takes a loss (absolutely or on average). OC, normally a losing sente is a mistake.
However, it is well known -- or should be --, that a losing sente can be a good sacrifice, made to prevent a gain by the opponent when she gets the move.
Now, the position in question is classified as a gote where the play gains 3 points. In that context, the descent is normally played with sente because it raises the local temperature, since it threatens the monkey jump. (As cdybeijing indicated.
) But, as Magicwand indicated, it is not a losing sente, since the response returns us to the same count that we started with. There is no sacrifice at all (on average). Once we have gotten this far, we can see that it is a possible play.
In the first example I showed the descent was not played with sente. The second example is more typical, where there is another gote play that gains 3 points. In such a case, playing the descent normally gets the last 3 point play (i. e., one that gains 3 pts.). That is so when there are an odd number of 3 point gote elsewhere on the board. Then playing the descent typically dominates playing the hane and connect. (Because zero is an even number, I expect that the descent dominates a significant percentage of the time, but less than half the time.)
Why, then, do the pros not seem to play the descent so often? There are a couple of reasons, I think. First, they learn that this is a 6 pt. gote. (It gains 3 pts. for White or 3 pts. for Black.
) Second, they correctly regard play values as mere guides, and use them to assist their reading, not to determine their play. So they will start out regarding it as a gote, and (I guess) only try the descent if the hane does not work out. Now, even though the descent often dominates, my educated guess is that it will make a difference between winning and losing once in 400 or 500 games. Since it matters so seldom, I think that the pros choose the prominent play the vast majority of the time.
OK, here's the twist. Suppose that there are an even number of 3 pt. moves elsewhere on the board and White should therefore play the hane in order to get the last one. Black may be able to prevent that beforehand by playing the descent herself. (Remember, it raises the local temperature. Black does not have to wait until the temperature drops to 3 to play the descent.)
Now, if it is foreseeable that one player, say, White, will get the move at temperature 3, then normally either White should play the descent in order to get the last 3 pt. play, or Black should play the descent beforehand to prevent that. I think that that is normally foreseeable, and that most of the time in a real game the descent is the normal play.
(And if it is not foreseeable, if you go ahead and play the descent before the temperature drops to 3, all you risk losing, as a rule, is a potential ko threat or the chance that your opponent will make a mistake.)
That will be the case in a gote position when each player has a non-losing sente.
(OC, not all third line hane and connect positions meet that criterion.)
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instead, assuming the follow-up monkey jump is sente?
White needs to settle the boundaries.