If those timelines are correct it then this is a massive question mark over the whole investigation. So NOONE called the police or anyone till 10.50? At that point, someone called the school who called Paul who called the police. So the dog was unattended for 70-80 minutes at the bench? When did the police arrive, say another 10-15 minutes.
The 10 minute window is ONLY based on the police theory that Nicola left her phone and the dog at the bench at 9.20. If she didn't, then there's a huge window of opportunity
And I still go back to the question of why no CCTV of Nicola on her walk has been released?