I really don't think that's the same thing. Taking multiple shots of the same subject is just taking a shot with a really long shutter time, except in slices, a little bit at a time.
What OP was talking about was something akin to using the noise in a photo of one subject to reduce noise in another photo of a completely different subject but with the same camera.
In astro-photography, this is quite common. You take a series of normal images. You then cover the the lens, and take the exact same exposure. After a series of processing, the noise pattern from the dark frames is subtracted from the normal images. It works quite well.
FWIW, some cameras can use that technique to help de-noise long exposure shots. The control image is a long exposure with the shutter closed, and that image (which should be completely black) is subtracted from the long exposure shots.
It's only the same as a really long shutter time if the subject is stationary, and in the case of Earth-based astrophotography it never is, because atmospheric turbulence is always moving the image. If you take multiple separate shots you can combine only the good ones:
What OP was talking about was something akin to using the noise in a photo of one subject to reduce noise in another photo of a completely different subject but with the same camera.
That works, to a point, but not great.