Distortion caused by saturation will be possible for certain configurations of the FFT. For instance, with TT_DATA=cint32, it is possible for the sample values within the FFT to grow beyond the range of int32 values. In the final stage when TP_SHIFT is applied, saturation is also applied. Similarly, if the FFT is configured for TT_DATA=cint16, but insufficient scaling (TP_SHIFT) is applied, then sample values may exceed the range of int16 and so these too will be saturated in the final stage.
Note that for cases with TP_PARALLEL_POWER>1, saturation is applied at the end of each subframe processor and also in each combiner, so for data sets which cause saturation even in the subframe processor, the output will likely not match the output of an FFT model.
For TT_DATA=cfloat, the FFT performs no scaling, nor saturation. Any saturation effects will be due to the atomic float operations returning positive infinity, negative infinity or NaN.