To be clear, I’m not strong at tsumego myself but wanted to add one thing…
TelegraphGo once live streamed a tsumego speed run from beginner up to nine dan without a single mistake!. What’s more, he did it on 101Weiqi which is by far the most difficult tsumego site imo. My point is that he is surely among the strongest amateur readers, and his comments should be taken seriously. He reckons that the first thing to do in any tsumego is to count liberties, and that if it seems that someone isn’t doing that it’s probably just because they’ve learnt to do it really quickly.
I don’t think that helps with the example problem, but perhaps in the future you’ll find it helpful. gl
To be frank I think the “beginner exercises” included as part of the OGS “Learn to play” sequence are very good as illustrations of a variety of different problem ideas, but are not very good as a beginner’s sole source of beginner problem material. This is in part for the reason you say, they ramp up in difficulty quickly and are a bit uneven, and also because the format is that you can click on one point and it either passes you or fails you. What a beginner often needs to do is play out the whole variation until they see why it fails or succeeds.
This image (from here) gives an example of what I would consider a better progression of beginner problems. They are all “black to move”, i.e. if black is surrounding, black should kill white, and if black is surrounded black should try to live. The first one is dead easy, the next one is harder but closely related to the first, and so on. There is no computer interface getting in your way, so you need to set them up on the board and play out all possible variations to understand them, or once you get stronger you visualize them all in your head (much better).
There are 18 problems that are slight, progressive variations on Problem 1 before they introduce a new variation on Problem 1 in Problem 19, and then there are ~12 variations on Problem 19 before they move on to a slightly different shape yet again, and so on. In this kind of problem book you will do hundreds of problems slowly introducing basic techniques one move at a time using variations on “standard” corner and side shapes before moving on to more free-form tactical problems that use those same techniques in arbitrary situations like the OGS problem that confused you.
