That is odd as I have usually found the exact opposite. For example, on the 5DIV, I often had to AF dark situations with DPAF as PDAF would not hit. I did not try that when I had the 1DX III. For a direct comparison, we would need someone that has both.

What I can say about the R5 is that I have not noticed an issue in low light. This includes shooting a couple of sunsets and sunrises as well as my usual sitting on the couch firing off a few shots around the living room that is only illuminated by the TV as I get to know the camera. It's AF rating is for -6 EV to +20 EV. Is there a specific scenario you are concerned about? If I can, I'll give it a try.

But, as a quick example, I was very surprised that the R5's AF picked up and AF'd Saturn and Jupiter for this shot.

Small-9040 by kayaker72, on Flickr

This is an insane crop, as I was only at 1000 mm. But I am not sure how much better I need than being able to AF on two little dots of light in an otherwise dark sky (there were little blue boxes around each). BTW, it was very winding with some high clouds. I think that caused some distortion.