Hi James,
While I can’t give you a definite answer (I suspect this isn’t documented anywhere), I would expect a DSLR to do a very good job of what you’re proposing. I would expect that the camera is doing intelligent downsampling and interpolation in silicon.
As I understand it, camera manufacturers see wannabe YouTubers who film themselves in dingy conditions as a huge market, and so they’re anxious to do low-light low-noise video well. They certainly wouldn’t be throwing data away. Thankfully for us astronomers, those are exactly the same requirements we have.
For what it’s worth, my partner has recently dragged me into filming ballet performances where the lighting is also sometimes far from ideal. I’ve been staggered by the video footage my Canon RP (and previously, 750D) can get of high-velocity dancers with hardly any light. By comparison, my Panasonic camcorder really struggles in low-light conditions.
Good luck,
Dominic