They have updated it
> Anthropic did post an official explanation, stating the original chart used a "simpler methodology" that "underestimated Sonnet 5's performance." The new chart supposedly uses their "standard methodology."
Oops!
https://www.reddit.com/r/ClaudeAI/comments/1ukgqwr/looks_lik...
The explanation Anthropic gave for the update doesn't address how the x-axis needed to range up to $50 previously and only $10 now. In any case the pass rates are also lower.
Probably the difference between whatever it is people notice when they say models become "nerfed".