SIGMA FP, DNG 12 bit, ISO test noise reduction capability

Many people talk about the native Sigma FP ISO, which is 100 and 3200. In fact, I did not see that there is less noise in the image at 3200 than at 1600, the noise increases as the iso increases. Surprisingly, even at very high values, noise is easily removed. Perhaps the matter is in a large amount of data 12 bits DNG. Lens: TTartisan 50mm f, 2 Music: Domitori Taranofu Deep Night