Did you read the article?
AI is a math & computer science problem. If AI can do advanced maths and computer science research, then it can begin to suggest useful algorithmic optimisations.
Right now I'm sure the vast majority of these will be junk, but occasionally, even with current limitations, they might occasionally stumble on something.
It's not really whether RSI is or isn't possible, it's really just whether it's the most efficient way for labs to improve their models today given they have limited compute to run AI-generated experiments and access to very intelligent humans who might have a better hit/miss ratio.
Do you disagree with anything I'm saying here? Do you not think current AIs can suggest algorithmic improvements or something?