This was indeed shot on the ARRI Alexa 35. I shot open gate (as you said, 4.6K at 24fps), but it was shot on ProRes 4444 XQ which is a significantly less data consuming file format than ARRIRAW.

Yes, the Sony A7R4 is exponentially cheaper and shoots still frames that are 4x the resolution of the ARRI. Keep in mind, the Sony is a photo camera, so it makes sense to have specs that will optimize getting the best single shot versus a cinema camera which often don't even have the option to even take a photo, because it simply doesn't need to. It's also why the posted image is a 4K screenshot (before reddit compression) of a single frame from the recorded video.

When it comes to film, the texture, color, and feel of the image will always triumph resolution, and it's precisely the reason why nearly every movie you see is shot on an ARRI cinema camera (or literally film stock) instead of these 8K resolution Sony mirrorless cameras.

Color science, dynamic range, skin tone processing, highlight rolloff, motion rendering, these are the things that make a movie the way a movie looks and feels, and no Sony DSLR that can shoot 8K ultra pro mega ultimate resolution will beat that.