I noticed it, there's definitely an improvement as I use my older Samsung devices as reference.
It's even noticeable when viewing on screen, before it use to look very patchy in mid to low light. Now it looks pretty much the same as my S20 Ultra. In fact a lot of photos in low light are almost identical to the S20 Ultra, with maybe a slight edge in sharpness to the S21.
In very low light however, night mode shots are the best. The near field details are incredible compared to previous Samsung cameras.
One area it's still lacking in low light now is 8k recording. It's very weak especially compared to the S20 Ultra, but I believe with the updates made to the 4k 60fps recording, they'll fix this in time.