On the first shots of the Su-57 prototype flight with the new engine, it immediately seems that the nozzle of the new TRD is shorter than that of the AL-100.
We see sawtooth edges to reduce radar visibility. Moreover, the size of the faces themselves is not less than the wavelength of the three-centimeter range X-band, which is used in the radar of the illumination and guidance of the majority of the air defense missile systems, as well as in the radar of the homing missiles.
It is obvious that this measure is intended primarily to reduce the visibility from the angle of exposure from below. After all, the usual edges of the nozzle flaps reflect significantly better.
Does it make sense to make the nozzle more compact? Yes there is. Such a nozzle is less noticeable in the infrared range, since it sticks out less because of the plumage.