Removing the "Market expert" which uses OHLCV (Open, High, Low, Close, Volume) also drops the sharpee from 5.01 to 1.88 while also increasing the max draw down to 13.29% (v.s. 9.70% for the index). I'd be very surprised if the pre training of the base model was the only source of leakage...
From paper: "testing set: January 1, 2023, to December 31, 2023"
From the Llama 2 doc: "(...) some tuning data is more recent, up to July 2023."