Because the limited information we know suggests that unless you believe Redwood was deliberately lying to the public.
DCI Redwood on Crimewatch Oct 2013
One of the things that we picked up very quickly was the fact that there was a night crèche that was operating from the main Ocean Club reception – and 8 families had left 11 children in there – and one particular family we spoke to us
gave us information that was really interesting and exciting. In fact, I would say it was – it was a revelation moment when, having discussed with them what hey were doing on the night, they themselves believed that they could be the Tanner sighting.
We’re almost certain, now, that this sighting is not the abductor. But very importantly, what it says is that from 9.15, we are able to allow the clock……to move forward and in doing so, things that have not been quite as significant or received quite the same degree of attention are now the centre of our focus.
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So the family gave the Met interesting & exciting information. Despite not being 100% sure Crecheman was really Tannerman, AR stated that, more importantly, it allowed the clock to move forward. That doesn't quite say Tannerman was eliminated but that something became more important than Tannerman. IMO.