Sir Husky Potato: I want to reformulate my question. What is the source for initial ranks for tsumegos?
d4rkm4tter: It takes into account the success/fail rate while considering the tsumego and the user rating. Here and in the other problem that you commented, the user only has to get one move right without understanding the concept. So it is ranked easier than other problems.
Sir Husky Potato: What is the reasoning behind a tsumego for 11 kyu (!) that requires a whole-board thinking and understanding of ko threats? This tsumego is nonsense for me. There are no ko threats to consider in order to start a ko. And 11 kyu player (which is heavily inflated in comparison to OGS) doesn't understand and doesn't need to understand this. Those low-level tsumegos are completely incomprehensible for me, I lost around 2 ranks thanks to them, as I always think that the answer should something different judging by the tsumego level.
I want to reformulate my question. What is the source for initial ranks for tsumegos?