I agree with that, Sadie.
The dogs were following a scent ~ but what that was is known only to them.
I think that because they did not follow the route taken by Tannerman the reckoning was that that sighting was not connected to Madeleine's disappearance.
How different history might have been had the dogs followed the Tannerman route to Crecheman's door or another car park. Murat might have been saved a lot of grief, Amaral might still have been in the PJ and the investigation might have followed a more positive line than it ultimately did.
I think we know a little bit more than that. There was some confusion, but whatever scent they followed seemed to have been on Madeleine's princess blanket and on a bath towel, according to the handlers who were given the items.
If [and I do mean if] that scent is what they found and followed they were following someone who;
handled both items
walked the path
crossed the road
stood by a lamp post next to the car park
visited the Tapas reception
went to 5H
went to or near 5J
went to 4G
didn't go to any other apartments in blocks 4 and 5