*edited to keep comment general, in light of recent developments.
I live on a busy south-facing main road, and our front door is set back from the pavement by about 5-6m (down the side of the building). You have to do a lot of trial and error with the setup of Ring so that it is not constantly activating/going off, and even with 'the perfect setup' you still get false/irrelevant alerts caused by shadows, moths, cobwebs etc. Everyone else on the street (terraced) has their front door straight out onto the public pavement - we seem to be the only users of Ring (or anything similar). Our next door neighbour installed CCTV over his front door, but it was quickly turned off and hasn't been used in years. Alert-based CCTV, in my experience, would be a nightmare if it was setup to catch all movement on the pavement and/or road. You would have thousands of clips a day to plough through just to check a parcel had actually been delivered (etc.)! I believe there may also be GDPR implications for privately-owned cameras setup to record public roads and pavements. Your phone battery, as well as the camera device battery (if used - most Ring doorbells are) would be exhausted, fast. Same with the paid cloud storage (30 days seems to only be a guide, if you have a shedload of clips you don't usually get the full 30 day history).
On this basis, I believe pcb has a strong theory. IMO it is unlikely a Ring cam was setup to capture general traffic moving in the area, looking at the general layout of residential properties vs pavements in the area. It suggests that SE and/or her attacker strayed closer to a residential property (whether on Poynders or nearby) than the pavement or main road. Personally, I do not foresee this footage being made public, I would imagine it could be quite valuable evidence at trial. All MOO, obviously.
