I must admit that I am not familiar with the SCN mode, nor any of the other specialized automati modes found in Rebel bodies. When I owned a Rebel, that mode was not available in its present form that you have described. Besides, after the first couple of days of owning the Rebel, I never tried to use any of the built-in automatic modes again.
I did not like the results that any of the Creative shooting modes were capturing. I could easily get better results using one of the Basic shooting modes, where I had more control over the capture process. The R5 is a semi-professional camera, which is probably why you are not able to find an equivalent automatic shooting mode. The R5 probably does not have them.
However, the behavior rhat you have described sounds very much like HDR shooting, which the camera can do. Most people who capture HDR images prefer to combine the images themselves, on a computer, instead of allowing the camera to do whatever it pleases.
There is no short answer to tell you how HDR image capture works, or why people use it. I suggest that you search YouTube for videos on the topic. Also, if you have not already downloaded a PDF of the full User Guide from the Canon web site, then I strongly encourage you to do it.
Again, there is no brief, concise answer to your question, which is probably why it has lingered for so long without any responses.
I agree that Handheld night scene mode is handy*, but a quick perusal of the R5 manual turned up empty. I guess you need a tripod.
*Waddizle: This mode allows you to use a higher shutter speed for nighttime shots. It takes 4 shots and combines them in camera.
12/05/2023: New firmware updates are available.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.