They might have been eliminated from the enquiry as you say, but they've not been added to the timeline. If someone did pass through at say 9:50am, didn't see anything odd, didn't see the dog tied up, didn't see anything odd at all - would they add this to the timeline or ignore it?
On the contrary, if someone did pass through around 9:50am and corroborated the witness statement by the lady who tied the dog up, that would be useful on the timeline, no? "Yes officer, I came through around 9:50am, saw the dog tied up, but thought nothing of it and continued on my way"... would be useful information. Would they include it on the timeline though?
My problem with it is that they are basing their whole time-frame on a single witness statement which doesnt appear to have been corroborated by anyone independent, only the daughter who received the call and the partner who came to the scene later. That's a red flag for me - I'd hope the police are trying to bottom that out, because without independent corroboration - the time-frame is more like 9:10-10:40.
All my opinion of course.