^^ Yes, he focused on the totem, because that's what the audience usually focuses on. Ever see The Prestige?
"Now you're looking for the secret... but you won't find it, because of course you're not really looking. You don't really want to know. You want to be fooled." 
The audience looks for the twist or the secret, because on the surface, that seems to excite or enthral us. By keeping the focus on the totem, one is able to "weed out" those who can't look past 
their perception of the film's ending and focus on the 
character and how he feels.
As mentioned, the point of the ending is that Cobb is finally in a place where he can accept any reality. What I really admire, though, is that the ending also poses the question, can 
we accept any reality, even one in which the protagonist is dreaming? Are we able to look past our personal beliefs/desires (ex: how can I be happy when I know that there remains the possibility that it is all a dream?) and side with the protagonist who we've just journeyed and connected with for the past 2.5 hours, or do we obsess about an answer (one that is not definitive, mind you) to a question that Cobb himself doesn't even care to answer? If we choose the latter, Cobb's initial obsession becomes our obsession, and by the end of the film, we are more trapped than he is. This type of connection with the audience, and discerning how a viewer relates to the character, is not possible without focusing on the totem.
Of course, spending a little time on the totem, I also like the argument that Cobb doesn't accept any reality, but rather becomes completely aware of the difference between reality and dreams. He spins the totem when he comes home strictly out of habit, but walks away from it because he is so sure of his surroundings. Cobb, after the whole inception ordeal, is confident in his reality, and believes that he returned home to his real children. When he hears there names being called, he snaps out of his habit of slaving over the totem, and instead chooses to rely on his thoughts and his feelings - he believes the world and his children to be real. This aligns with the interesting idea of trusting what we feel and see vs. what we see. Does not Cobb not need the totem anymore because, now over Mal, he is so confident in his perception of reality, or is it because (as discussed in my above interpretation) he has come to accept that one can find happiness, solace and catharsis, even in a dream? If one were to choose the latter option, what does that say about Cobb and his children? If part of him believes that it doesn't matter whether or not he is in a dream, then what of his children in the real world? How does he cope with that slim possibility of leaving his kids behind? Of course, I'm sure had the film not cut to black, Cobb would have turned around eventually...unless of course he just picked up his kids and kept on walking towards the sunset... 

 Anyhow, I think both sides, and the entire argument, are all quite compelling, especially when dealing with such a flawed character. Does he have the right to give in and be a little selfish? Should we reward that? Is he too confident in his skills of perception? Etc. etc. etc. 
 
 
t: 
So, that's just my (loooong) take, and that's why I love it. I like asking people who've seen the movie what they felt the most important part was of the ending/their take on the totem, simply because I'm interested in hearing how many people answer "he walked away without looking." It's always fun to hear the different ways it resonated with viewers, and what they took away from it. 
