I assume it's already been proposed here before so I hesitate to say it. But the other option for the Met not resolving the issue of why Totman would be walking in that direction is because they don't actually believe that he did. Instead, Redwood's assumption is that Jane is mistaken in her recollection of which way the man was going.
The mind can play tricks. Redwood may have concluded that Jane recalling seeing a man, after Madeleine had just been seemingly abducted, might have caused her recollection to become influenced/muddled about what she actually saw. The same as Martin Smith's recollection possibly was when he learned that Gerry had been made Arguido.
To be clear, I'm NOT necessarily saying that's what "I" think happened to Jane, before anyone tries putting words in my mouth. I'm just saying that "IF" the Met were indeed working on this assumption, it could also explain a few other things.
1. It could explain why the Portuguese authorites so quickly dismissed Totman as being Tannerman. If he'd said he was definitely heading towards the apartment block with his daughter, and never away from it as Jane described, he may have been ruled out on that basis. As inadequate as their investigation was, it is strange they would not have followed this up at any point, given it was their main lead at the time. Or later on, when it would have suited them down to the ground to have assigned Totman to being the man Jane saw.
2. It could explain why the McCanns have never committed to Totman being the person Jane saw. And why they, nor Jane, have made any comment about it. Despite Redwood being "almost" certain, they don't appear to agree. The drawings of Tannerman are still displayed prominently on their website and they state that while "the Met" believe this man "may" be another guest, it is "not certain" that it's the same person.
3. It could explain why neither the Met or the Totmans have offered any explanation as to why he was walking in that direction. The Totmans provided comments to the press and could have explained about the route he walked and at what time this was, but they offered up no details at all. All Redwood would commit to was that Mr Totman was walking "near" the apartment. He doesn't say at what time and I think if they "had" ascertained that he had walked in the direction Jane described, they would/should have said something about it IMO. If their assumption was that Jane was incorrect in her memories, I think that would be something that none of them would want to particularly broadcast though. It would only raise more doubts, questions and criticism if they were working on the assumption that Jane was wrong about what she saw. It would also undermine their promotion of the Smith sighting as a new angle of focus.
4. It could explain why the Totmans never contacted police during the 6 years before Redwood's team got in touch with the night creche families directly. If the Totmans strongly believed he could have been that person, you'd think they would have done a bit more to come forward, rather than just waiting to "hear back" as his wife put it. It could be that it's because he knows he wasn't walking in that direction at all and so, either it wasn't him, or he would have to claim Jane's account was wrong.
IMO, the assignation of Totman being Tannerman is inconclusive.
Going back to CB though, I thought it quite interesting that the BKA are seemingly placing no interest on the Smith sighting. Martin Smith says he didn't even find out about CB until it came out in the papers. Given how much the BKA 'appear' to want to place CB in the area, you would have thought they (or SY on their behalf) might have at least approached the Smiths with a photo of CB to see if it rang any bells prior to the appeal. I just wonder if they perhaps have other intel about the course of events that night which allows them to consider this event redundant.