It is and I have corrected it (At the current time I am doing a lot of Keeppower cells).
The typical cell rating requires a specific temperature for charge and discharge and charge may be with a lower termination current than I use and is usually also to a lower voltage than I do. All this together can explain some difference.
It may be a rewrap or a Chinese cell, some China factories are getting very good at making LiIon batteries.
This is a discharge rate enhanced Samsung 30Q; the shape of the discharge curves match, its top too. Versus a 30Q its internal resistance is lower, while its capacity is a little bit lower. This allows the cell to meet a 20A continuous discharge rating without exceeding 80°C (at 25°C ambient).