Why DeFi agents can't be trained on on-chain P&L alone: adjust σ (ETH's real 3.46% daily vol) and edge α to see how many trades you need for 95% confidence, and how process rewards cut it 10×. Math RL reaches certainty in 7 episodes; DeFi takes 4,600.
ETH's 3.46% daily volatility buries a 0.1% trading edge so deeply that on-chain P&L needs 4,600 trades — 230 days — before you can tell skill from luck at 95% confidence. Process rewards fix it in 23.