I think that there are times when people take a photo in which the subject is underexposed, then they raise the exposure in post, and wonder why it is grainy, or think the camera is "bad at noise grain".
Of course, this is an unrealistic way for people to go about photographing things if they expect to get excellent results. . The exposure should be set to expose the subject properly so that it doesn't need to be brightened in post. . Only then can they evaluate the noise characteristics of a camera fairly.
That's correct. With 90D, I found that getting the proper exposure in camera is more critical because underexposed images are much harder to correct in PP. That's a huge challenge, though, for bird photographers faced with the lighting conditions changing so rapidly -- even with the Auto ISO with exposure compensation adjustment.