This is not the only paper that scales reasoning complexity / difficulty.
The CogniLoad benchmark does this as well (in addition to scaling reasoning length and distractor ratio). Requiring the LLM to purely reason based on what is in the context (i.e. not based on the information its pretrained on), it finds that reasoning performance decreases significantly as problems get harder (i.e. require the LLM to hold more information in its hidden state simultaneously), but the bigger challenge for them is length.
Perhaps some people are offended by this argument, but it's definitely worthy of a discussion instead of censorship.