Strange dependence of the image processing result on the DPI value of the same source file

I noticed that programs that work with graphics are strangely related to the DPI of the source files.
For example, Denoise AI is generally not able to correctly remove noise from black-and-white images with a DPI value of 3600, obtained from a film scanner.
If you manually change the DPI value to 300, the program becomes more correct. But you still have to manually select the DPI value each time.
This shouldn’t be happening. The information about the DPI is intended for the printer and should not affect the result of image processing.
Regarding Gigapixel AI, it independently changes the DPI value to 72, regardless of the DPI of the original images.