You are correct. The GFI does protect humans from current leakage and circuits from accidental current leakage, say, if a tool being used has a current draw leg imbalance.
Re: a shock , always wear rubber shoes and work with one hand ( said to limit shock to few inches in fingers), can work with 2 hands live wire with proper rubbers matting to stand on and proper insulated gloves , but may need some "active" training, to test limits of this protection..
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