By the time they were Madeleine's age my children were dressing and undressing themselves, the only problem for them being shoe laces.
In my opinion the cite I used demands almost clinical conditions for a scent source which must be almost impossible to achieve under normal circumstances.
I think the most logical scent source for the dogs was Madeleine's blanket with other contaminating scents being overridden by the strongest, which must have been hers.
The witness sighting was discarded without further investigation when it was found that it did not fit the senior investigator's then working hypothesis. The information used by Scotland Yard to "almost certainly" rule it out was available to that investigation in 2007.
The fact that it was at a remove of seven years that a foreign force "managed to reach the correct conclusion" using information available to the original investigators is a measure of the incompetence which evidences their neglect of elementary procedure.
The blanket was indeed the best source, but it wasn't offered to the best qualified dog, for unknown reasons. Nevertheless the towel provided produced the same result. That suggests;
The child's scent was on both items
Someone else's scent was on both items
There were different scents on the items, but both came from people who followed that route together or separately.
Jane Tanner's evidence was not highly regarded by the PJ, but not for the reasons you give. Do you have evidence that information used by SY was available to the PJ in 2007?