I'm concentrating on one alert only, in the main bedroom. As I understand it Eddie gave a positive alert with his head in the air. This means he was alerting to the scent he was trained to find, but couldn't give the source of it. It wasn't blood so what was it? If it was cadaver scent where did it come from? Grime mentions a number of possible scenarios but doesn't elaborate as to what they might be. There may be no evidence to explain his alert, but the alert occurred.
Even so your quotes misrepresent the actual statements in one particular direction, removing in each case the caveats made in context.
These are facts about all dog alerts:
Dogs are trained to respond to certain odours.
All dogs are liable to false positives and false negatives- may alert where there is no target odour and fail to alert to the presence of the target odour.
Alerts are only indications, not finding of fact.
Their accuracy is mixed depending on their training and the type of detection.